Quitting the European Union risks turning the North into a 1980s-style wasteland and leaving the UK's largest cities facing "serious economic danger", Labour will warn.
In a day of intensive campaigning to win over wavering party supporters, Gordon Brown and Neil Kinnock and the leaders of the largest councils outside London will insist that working people would be hit hardest by Brexit.
Leave supporters Boris Johnson and Michael Gove will continue to focus on immigration with a letter calling on David Cameron to issue a guarantee about Turkey's future in the EU.
They will also call on the Prime Minister to say if he has given up pushing for further changes on freedom of movement after his most senior Cabinet ministers appeared to be at odds over reform.
Mr Brown and Lord Kinnock, along with the Labour leaders of the UK's 10 biggest cities after the English capital - Birmingham, Bristol, Cardiff, Glasgow, Leeds, Liverpool, Manchester, Newcastle, Nottingham and Sheffield - will issue a stark warning about a post-Brexit future.
The Core Cities group says: "Leaving would be a grave threat to our local economies, risking people's jobs and livelihoods.
"If we vote for Brexit, it will be those at the sharp end - working people, not the leaders of the Leave campaign - who will pay the price.
"For those that believe the EU can work better for Britain, we agree, but people must choose reform, not retreat.
"A vote for Remain is a vote for prosperity and progress for Britain's cities. A vote to Leave is a vote for serious economic danger. It is simply not worth the risk."
Vote Leave said Britain's cities would benefit from the cash saved by no longer paying into EU coffers.
Chief executive Matthew Elliott said: "These are desperate times for the In campaign - recycling a declaration of support that was first made in February and then repeated again in April.
"The truth is that the UK's cities have prospered in spite of our EU membership, not because of it.
"Every week we send £350 million to the EU, enough to build a fully staffed NHS hospital. Our cities would benefit hugely if we took back control of this money and spent it on our priorities - such as public services and infrastructure - instead."
The North benefits from Britain being in Europe through more jobs, exports, inward investment and spending on education and infrastructure, according to Labour.
Mr Brown will hit the campaign trail to warn that "Tory Brexiteers" will turn "our industrial heartlands into industrial wastelands".
Lord Kinnock will insist that Tories Mr Johnson and Mr Gove will not transform from the Sheriff of Nottingham into Robin Hood.
"The sharp warning of a recession caused by the shock and instability of quitting Europe is serious and realistic," the former Labour leader will say.
"It is the sort of risk analysis that everyone does before buying a car or a house - and is vital as we decide the future of our country and our children.
"If Britain votes to leave the EU, Boris Johnson and Michael Gove will have power. They are never going to change from being the Sheriff of Nottingham to Robin Hood. They would use the damage to the economy as an alibi, an excuse, for deeper, wider "austerity". Working class people will be hit hardest."