The British government has said claims from Gerry Adams that Brexit will destroy the Good Friday Agreement "are totally without any basis in fact".
The Sinn Féin President has alleged that fundamental human rights enshrined in the 1998 accord to end violence could be undermined, in an address on Saturday.
A statement from the government yesterday said none of the institutions and provisions set out in the Belfast Agreement, including those relating to human rights, are in any way undermined by the decision of the UK to leave the EU.
It also re-iterated Theresa May's position that there will be no return to the "borders of the past".
"These comments are totally without any basis in fact," the government said.
"The UK Government is fully behind the implementation of the Belfast Agreement and its successors, including Stormont House and Fresh Start. There will be no return to the borders of the past.
"We are also working intensively to ensure that following the forthcoming election strong and stable devolved government that works for everyone is re-established in Northern Ireland."
In his address at a Sinn Féin conference Mr Adams said the British Government's intention to take the North out of the EU, despite the wish of the people to remain, is a "hostile action".
"Not just because of the implications of a hard border on this island, but also because of its negative impact on the Good Friday Agreement.
"The British Prime Minister repeated her intention to bring an end to the jurisdiction of the European Court.
"Along with her commitment to remove Britain from the European Convention on Human Rights, this stand threatens to undermine the fundamental human rights elements of the Good Friday Agreement," he added.
Meanwhile a former senior member of the European Commision has claimed Irish border controls will return post-Brexit.
Michael Lux, the former head of the Commision's customs procedures unit has said "red and green lanes" could be introduced as a form of customs control.
"So there would be two lanes for vehicles; a green one where you are only occasionally stopped and a red lane if you carry goods above the threshold," he told the BBC's Inside Business programme.
Mr Lux has suggested that the current model that exists on the Norwegian-Swedish border could be recreated.
British Prime Minister Theresa May has said does not wish to see a hard border return on the island of Ireland, but stated Brexit means leaving the European Union Customs Union (EUCU)
Under EUCU law tariff and paperwork-free trade is permitted between Northern Ireland and the Republic of Ireland. On Friday, Taoiseach Enda Kenny told RTÉ that "papers are being prepared" on ways to minimise border customs checks,
Former First Minister Arlene Foster said last year she could not foresee a time when heavy goods vehicles would be stopped and searched post-Brexit, but Mr Lux said it was unrealistic not to expect border delays.
"Yes it can be done electronically with an export declaration, but from time to time, there must be controls," he added.
