Tony Blair has praised former political enemies who have put aside their differences to campaign for a second Brexit referendum.
And tonight he was due to tell an audience in London: "Five words I never thought I'd say - thank God for John Major!"
The former Labour Prime Minister was due to appear at a rally calling on voters to choose candidates backing a second referendum after the former Tory PM appeared by video link.
It comes after Mr Major made a bombshell intervention calling on the electorate to back former Tory ministers David Gauke, Dominic Grieve and Anne Milton, who were booted out by Boris Johnson .
The trio are standing as independents against Conservative candidates.
Despite being leader of the opposition when Mr Major was in Number 10 the two former PMs have set aside their party differences to back a "People's Vote".
He told an audience in Blackfriars, London: "Here are 5 words I never thought I would say: Thank God for John Major.
"To John, to Michael Heseltine: for years I stood against you; tonight, it is an honour to stand with you.
"And to David Gauke and many others, good, smart, capable people across the political spectrum prepared to speak out, to put country before Party and principle before position: your courage is an example. It is a tragic commentary on the state of the nation that those whose voices we need most in our politics are in greatest danger of being silenced."
Sir John, who led the Conservative Party between 1990 and 1997, is backing rebel candidates standing against Boris Johnson loyalists in a hammer blow for Boris Johnson.
It comes after Lord Heseltine said lifelong Tory voters should back the Lib Dems in order to stop Mr Johnson's Brexit .
Mr Blair, who has already called on voters to deny either Jeremy Corbyn or Boris Johnson a majority, told the audience: "Its not one General Election but 650 individual ones.
"There are great Labour candidates who deserve whole-hearted support. I am voting Labour.
"But let me put it this way. If you look, constituency by constituency, you will know the best candidates to back. Back them!"
"It will make our country poorer and weaker. It will hurt most those who have least.
"Never have the stakes been higher, especially for the young. Brexit may even break up our historic United Kingdom.”
Sir John will endorse the three former ministers, who were expelled by Mr Johnson in September, stating: “Let me make one thing absolutely clear: none of them has left the Conservative Party, the Conservative Party has left them.
"Without such talent on its benches, Parliament will be the poorer, which is why – if I were resident in any one of their constituencies – they would have my vote.”
Sir John described Brexit as “the worst foreign policy decision in my lifetime", saying: “It will affect nearly every single aspect of our lives for many decades to come.
