Secretary of State Chris Heaton-Harris has said he intends to establish an independent statutory inquiry into the 1998 Omagh bombing.
The dissident republican bomb exploded in the Co Tyrone town on August 15, 1998 killing 29 people, including a woman pregnant with twins. Hundreds more were injured.
In 2021, a High Court judge recommended that the British government should carry out a human rights-compliant investigation into alleged security failings in the lead-up to the attack.
Mr Justice Horner found that it was potentially plausible the attack could have been prevented.
- Omagh bombing in detail
Mr Heaton Harris told MPs today: "I have listened to the representations of these families and taken their varying perspectives into account. I have considered important factors such as the independence of any future investigation, the costs to the public purse and how best to allay wider public concern.
"I have weighed these up against the clear findings set out by the court, which we must meet for any investigation to be effective and compliant with our international obligations, and which are at the core of my decision.
"I intend to establish an independent statutory inquiry into the Omagh bombing.
"I have informed Mr (Michael) Gallagher and members of the Omagh Support and Self Help Group, as well as representatives of Families Moving On, of this decision."
Mr Heaton Harris said the inquiry "will focus on the four grounds, which the court held, as giving rise to plausible arguments that the bombing could have been prevented".
He went on: "I know that this is a significant decision and I'm keen to explain now to the House why I believe it is also the most appropriate course of action.
"Firstly, the inquiry will allow us to meet our Article 2 procedural obligations under the European Convention on Human Rights as it will have powers of compulsion and be capable of compelling the production of documents and witnesses and subjecting their accounts to scrutiny."
Mr Heaton-Harris noted the 2008 review conducted by Sir Peter Gibson did not have such statutory powers, meaning he had "no means of compelling witness testimony".
He went on: "It's important that any investigation has sufficient tools at its disposal to access all necessary evidence and materials."
The secretary of state said it is not in his power to call for "a simultaneous Article 2 compliance investigation" in the Republic.
Chris Heaton-Harris told the Commons: "The inquiry will involve the next of kin and will be open to public scrutiny where possible.
"This will of course, need to be balanced against national security considerations. And it's important to note that there will be some material, which will not be able to be examined in public. A final report will be published which will respond to each of the issues identified by the High Court.
"You may be aware that in his judgment, Justice Horner expressed a desire that a simultaneous Article 2 compliance investigation occur in Ireland.
"He recognised that it was not in the court's power to order a cross-border investigation and nor it is in my power as secretary of state for Northern Ireland to do so.
"But I remain in contact in close contact with the Irish government on this issue."
Mr Heaton Harris said he hopes his decision will give "some comfort" to the families who have "have long campaigned for this outcome".
He told MPs: "I wish to assure the House that this decision has been taken following careful consideration of the facts, the findings of the Supreme Court judgment and the United Kingdom's obligations under Article 2 of the European Convention on Human Rights.
"I hope the decision to establish an independent statutory inquiry gives some comfort to those families who have long campaigned for this outcome. I recognise however, that not all families affected by the bombing desire such further investigation.
"Some have worked hard to process their trauma and to move on with their lives and do not wish to re-examine the past. I hope that the targeted nature of the inquiry to allow it to answer the four points I mentioned earlier will provide the middle ground."
Mr Heaton-Harris said his next steps are now "proceeding to identify a chair for the inquiry" and to "finalise the terms of reference following consultation with the chair".
He went on: "My intention is that the terms of reference will be heavily based on the grounds set out by the court. Further details will be announced in due course but it's my full intention to establish the inquiry as promptly as possible for the investigation to proceed at pace."
The Labour Party's shadow secretary of state Peter Kyle told the Commons: "We welcome the decision by the Secretary of State that he has made, and the approach that he has taken in putting the victims first in his deliberations.
"I know that he met with families before Christmas. I know that he promised that he would return personally to tell them whether he would order an inquiry. He has been a man of his word."
He added: "It's important to say that if the inquiry finds shortcomings in how the intelligence was used, it will not change the fact that it was republican terrorists who are ultimately responsible for the lives lost and changed that day.
"Any Article 2 compliant inquiry should provide the opportunity to learn the lessons that will prevent similar tragedies into the future.
"The Republic of Ireland now has a moral obligation to start their own investigation."
Mr Kyle said there is a "clash" between the decision to order an inquiry into the bombing and the approach to other Troubles legacy issues.
He told the Commons: "The fact the Secretary of State is calling for this inquiry does clash with the Government's overall approach to legacy issues. We oppose the Government's Legacy Bill because it provides more benefits to perpetrators than it does to victims of terror.
"The Secretary of State has put Omagh families at the heart of today's decision. I'm worried that other victims of atrocities during the Troubles will be watching and wondering why their loved ones are not being treated in a similar way?"
He added: "A seesaw approach to policy isn't healthy in any circumstances, but least of all when dealing with the sensitivities of Northern Ireland's past. The Government has presented its logic as to why the atrocities committed in late 1998 qualify for a public inquiry, and those before don't.
"But it's a logic only understood within Whitehall. Many families... simply cannot see the logic of why the crimes that shattered their lives are undeserving of similar treatment to that announced today."
He went on: "If he (Northern Ireland Secretary Chris Heaton-Harris) is proceeding with a legacy approach he has inherited, he needs to be certain that it will provide the same comfort to and answers to all victims that he is offering the families of Omagh today."
DUP Strangford MP Jim Shannon told the Commons: "I remember exactly where I was the day that the Omagh bomb atrocity took place and I remember the news being announced as well. It is a day back in August 1998 when we really appreciate all the efforts today.
"My party has previously supported the Omagh families' call for an Article 2-compliant investigation and I very much welcome the Secretary of State's announcement today."
Mr Shannon said that the bombing was "planned and assembled and transported from within the Republic of Ireland", and called for the government there to set up a similar inquiry, adding: "Would the Secretary of State agree that unless there is such an investigation it is unlikely that the full truth about what happened that day will be brought to light?"
Mr Heaton Harris told MPs that the British government could not compel the Irish government to open an investigation.
But he added: "We are talking to each other on a whole range of different issues in a much more constructive way than we have done for a decent while, and I know we will have - actually some of the discussions on things like this can be quite tough on both sides - but they are being done in a respectful way and I know that both sides are wanting to do the best by all the people that we represent."
Mr Heaton Harris said he hoped an inquiry would give Michael Gallagher, the father of one of the Omagh bombing victims, "as much information about what happened that day as possible".
Responding to Labour in the Commons, Mr Heaton-Harris said: "I actually do believe that we are being consistent. What has happened is that for hundreds, if not thousands of families, 25 years since the Troubles ceased and the Belfast Good Friday Agreement came into effect, there has been no justice and no information about what happened to their loved ones in that period of time.
"Investigations might have come and gone, but to no result for those families. And what the Legacy Bill hopes to do - and as he knows I am trying to improve the Bill as much as possible - to try and make sure that we get the Legacy Bill into exactly the right place so it can give those families, if at all possible, at least some information about what happened to their loved ones at this time.
"Which is all, actually, I think, Michael Gallagher really wanted when he started his campaign. He wanted to know as much information about what happened that day as possible. And I really do hope that the inquiry I have announced today will give that to him."
Alliance MP Stephen Farry asked the secretary of state to respond to Michael Gallagher, whose 21-year-old son Aiden died in the 1998 bombing.
He told the Commons that Mr Gallagher believed there were "serious security and intelligence failings" and that the bombing was preventable.
The North Down MP added: "Can I also ask the secretary of state just to confirm the terms of the terms of reference that he has set out.
"Comprehensive though they were, if the chair feels he needs to go beyond that, that he will have the flexibility in that respect?"
Mr Heaton Harris replied: "I completely understand Mr Gallagher's point but that information will come to light in this inquiry, I am absolutely sure, if it exists, so I hope that he will be able to prove himself, and the community in Omagh, and the wider community too, one way or the other exactly what happened.
"As to the terms of reference actually they are not set yet, and when I have appointed the chair of the inquiry I will get to that conversation, but I will certainly take into regard what he has just said."
Former secretary of state Theresa Villiers told the Commons: "The Omagh bomb was one of the most appalling atrocities of the long campaign of terrorism in Northern Ireland and, even all these years later, it is still painful to hear those facts recounted at the despatch box in this chamber.
"I accept the decision that the secretary of state has made; it is different to one that I made but I accept that circumstances have changed and I believe it is important that in this inquiry going ahead we need to address some of the defects in the public inquiry process."
She added: "We want to avoid the delays that have beset some public inquiries, we want to ensure that the extensive investigations that have already taken place into the Omagh attack are carefully considered by this new inquiry.
"Of course, as the secretary of state has said, it is vital that sensitive security information can be examined by the inquiry but not disclosed publicly in a way which would put lives at risk or jeopardise the fight against terrorism."
Mr Justice Horner's ruling in 2021 came after a legal challenge by a bereaved family member against the government’s refusal to hold a public inquiry.
The judge also recommended that the Dublin government establish its own investigation.
Mr Heaton Harris had pledged to announce the Britisg government’s response to the judgment early in the new year.
The secretary of state travelled to Omagh in December to meet some of the bereaved families and visit the site of the bombing and a nearby memorial garden.
In his 2021 judgment, Justice Horner directed that a fresh investigation should take place into the Real IRA atrocity.
He said any probe should examine the failure to act on an informer tip-off or use intelligence and surveillance evidence about previous terror attacks.
The judge said a new investigation should also examine whether a politically motivated “de-escalation” of the security approach to dissident republicans in the months before the 1998 attack resulted in crucial intelligence not being acted upon.
Mr Justice Horner said he was not going to order specifically that the UK probe into the Omagh bomb takes the form of a public inquiry, explaining he did not want to be “prescriptive” about the methodology.
While having no jurisdiction to order the Irish Government to act on the matter, the judge also urged authorities there to establish their own probe in light of his findings.