Jeremy Corbyn will tomorrow promise to reinvest the UK's EU budget contributions into public services after Brexit.
In a line which echoes the Vote Leave campaign's pledge on NHS funding, Mr Corbyn will say: “We will use funds returned from Brussels after Brexit to invest in our public services and jobs of the future, not tax cuts for the richest."
But the Labour leader will also mock Brexiteers who suggested the budget contributions could be used to invest in the health services.
“We’ll give the NHS resources it needs as we will raise tax on those with the broadest shoulders to pay for it - not by making up numbers and parading them on the side of a bus.”
And he will strike an ambivalent tone about the future outside the EU, saying: “The EU is not the root of all our problems, and leaving it will not solve all our problems.
"Likewise the EU is not the source of all enlightenment, and leaving it does not inevitably spell doom for our country. Brexit is what we make of it together.”
Reports suggest he will also use a speech tomorrow to formally back staying in a customs union with the EU.
It comes after more than 80 Labour figures signed a letter urging the party leadership to back remaining in the European Economic Area "as a minimum" after Brexit.
The Mail on Sunday quotes a Labour insider saying that John McDonnell persuaded Mr Corbyn to make the move to try to force an early general election.
"McDonnell basically said that May was on the hook over the customs union and this was too good an opportunity to miss."
Elsewhere, the Sunday Times details how Cabinet ministers warned Theresa May that pro-European Tory rebels could put her premiership at risk by uniting with Labour over the issue.