FORMER Tory MP Michael Portillo believes Boris Johnson as British prime minister will negotiate a Northern Ireland-only Brexit backstop – and will hold a referendum in the north to secure support for the plan.

The former Conservative leadership contender has for years been against Mr Johnson leading the party, but said he now feels a "sort of enthusiasm that he is going to win by a landslide".

Mr Johnson is the frontrunner to succeed Theresa May as leader of the Conservative Party and become the next British prime minister.

Speaking on BBC's This Week programme, Mr Portillo made a prediction on how he thinks Mr Johnson would resolve the UK's Brexit deadlock.

"Theresa May was offered a backstop that applied only to Northern Ireland, and she got worried about that because she thought that separated Northern Ireland from the rest of the United Kingdom," he said.

"She insisted on a backstop that involved the whole of the United Kingdom. That then set the Brexiteers against her, because they said now we're locked into a permanent Customs Union.

"The way out of this is to go back to the Northern Ireland-only backstop and to obtain the consent of the Northern Ireland people, I would say through a referendum in Northern Ireland.

"They will give it, I think, because they don't want to go back to a border, and they want to have free trade with the Republic."

This Week presenter Andrew Neil pointed out that "Mr Johnson isn't talking about any of this", to which Mr Portillo replied: "No I know, but he'll get there."

The Brexit deadline was pushed back to October after MPs on three occasions rejected Mrs May's proposed withdrawal agreement on leaving the European Union.

Most Tory leadership contenders are proposing changes to the backstop – the much-disputed arrangement aimed at guaranteeing no hard border in Ireland if no alternative plan is agreed between the UK and EU.

However, the EU has insisted it will not reopen the proposed withdrawal agreement negotiated with Mrs May.

Meanwhile, DUP MP Jeffrey Donaldson said he does not think Taoiseach Leo Varadkar is "acting in Ireland's interests" because a no-deal Brexit seems likely unless the UK's backstop concerns are addressed.

Mr Donaldson yesterday told RTÉ a timescale for the backstop is needed to put MPs' concerns at ease.

"I disagree that the taoiseach is acting in Ireland's interests, when he knows that we are heading towards a no-deal outcome unless we can address the concern about the backstop, and the timescale for the backstop," he said.

"I don't think that it is a huge ask at the end of the day to avoid a no-deal outcome," he added.