Leading figures in the campaign to keep Britain in the EU have admitted they got it wrong on immigration but warned Theresa May she will convert “defeat into a tragedy” if she cuts Britain off from the world.

Three former ministers — one from each of the main parties — whose own constituents voted to leave the EU joined forces this weekend to pile pressure on the prime minister to secure the best possible trade deal with Brussels.

Writing in The Sunday Times, Anna Soubry, a Conservative, Labour’s Pat McFadden and the Liberal Democrat Norman Lamb concede the “free movement of people cannot continue as it has done” but warn against “pulling up the drawbridge”.

They say the referendum result “was not an expression of