John McDonnell has risked antagonising the Democratic Unionist Party by declaring that he longs for a united Ireland.
The shadow chancellor reaffirmed his pro-Republican views as he warned against Brexit negotiations damaging the Good Friday Agreement.
Mr McDonnell, speaking to political journalists at Westminster, said in response to a question: “You know my background: I’m a Republican. I long for a united Ireland but I recognise democracy.
“Ireland will not be reunited on the basis of some contortion in the relationship with the EU.
“It will only be reunited on the basis of the popular support of the Irish people. That’s what I respect.
“One of the concerns we have got through all this on all sides of the Republican debate is that nothing in these discussions should cause any damage to the Good Friday Agreement, which I think was a huge achievement.”
Mr McDonnell’s remarks are likely to harden the opposition of the DUP, currently propping up the Conservatives in the Commons, to a general election that could lead to a Jeremy Corbyn government.
The veteran left-winger, 67, who was a serial rebel during Tony Blair’s government from 1997-2007, also paid a rare tribute to Mr Blair for negotiating the Good Friday Agreement.
“I say this about Tony Blair,” he said. “I was a critic of his on Iraq and a whole range of other issues. But if he’d have stopped at Northern Ireland he’d have gone down in history as one of the most significant prime ministers in our history.
“To bring about peace in Northern Ireland in that way was a huge achievement and I’ll always respect him for that.”
And he joked: “There will be some curious relationships that come out of a general election. If I can get my application in for the Orange Order and order my bowler hat and sash for the marching season, you never know.”
During his speech, Mr McDonnell claimed Labour could be in government “within months” and said: “This is not a government going out with a bang, but going out with a whisper.”
He also reaffirmed the Labour Brexit policy passed at its Liverpool conference, predicting the party could end up supporting another EU referendum if Mrs May is unable to get a deal through Parliament.
“If a deal comes back that protects jobs, then yes we’ll support it,” he said. “If it doesn’t, we will vote against and we’ll call for a general election.
“If there isn’t a general election, we’ll have a fallback position and there might well be a people’s vote of some sort.”
He accused the Government of “two wasted years” on Brexit and predicted the outcome of Brexit negotiations would be a “fudge”.
On Brexit crowding out other Commons business, he said: “The Tories are in office but not in power.”
And on Tory splits he said: “Conservative MPs hate each other more than they hate us.”
(c) Sky News 2018: Shadow chancellor John McDonnell reaffirms support for united Ireland