Jeremy Corbyn will be among numerous Labour grandees involved with the party's day of action across the UK on 21 June, as the EU referendum looms. The left-winger will appear alongside Labour In for Britain chair Alan Johnson in Manchester, where Corbyn is expected to warn that a Brexit would put workers' rights and jobs at risk.

"These next hours will shape Britain's future for years to come," he will argue. "For all the arguments of recent weeks, this Thursday's decision can be boiled down to one crucial question: what's best for jobs in Britain, rights at work and our future prosperity?

"On 23rd June we are faced with a choice: do we remain to protect jobs and prosperity in Britain that depend on trade with Europe?

"Or do we step into an unknown future with Leave, where a Tory-led Brexit risks economic recovery and threatens a bonfire of employment rights? A vote for Remain is a vote to put our economy first. On Thursday join me in voting remain to protect jobs and rights at work."

Former Labour leaders Lord Neil Kinnock, Ed Miliband and Gordon Brown will also appear at pro-EU events during the day of action, with Brown in Glasgow, Kinnock in Cardiff and Miliband joined by Harriet Harman in Birmingham.

The rallying call is designed to drum-up support from Labour voters, who are expected to be crucial in the referendum result. But some Labour MPs, such as Gisela Stuart, Frank Field and Kate Hoey, are backing a Leave vote on 23 June. Stuart, the chair of Vote Leave, has warned that the EU is unreformable.

"For years, British governments have tried to be pragmatic about Europe. They have taken the view that you can always kick the big decisions down the road. Well, now the time has come to decide," she wrote in an IBTimes UK blog.

"If the EU were an energy supplier or a bank, you would long ago have stopped believing its marketing, you would have seen it was hopeless value for money and never listened to its customers. You would just move your account.

"It is time for Britain to recognise that Brussels has had enough chances. And that the only safe option is to Vote Leave."

The latest opinion polls have showed a shift to Remain ahead of the 23 June vote, with a survey from Survation, of more than 1,000 people between 17 and 18 June, putting Remain on 45% (+3) and Leave on 42% (-3). Meanwhile, bookmaker William Hill have made Remain 3/10 favourite (76.9% chance), with Leave offered at 5/2 (28.5% chance).