Remaining in the EU is crucial to defend investment, jobs and workers' rights, Labour's leader Jeremy Corbyn has said.
Speaking at the launch of Labour's short campaign, Corbyn said that there is a crucial choice on the 23 June on whether to remain in the EU and reform it or to walk away from it.
"I believe we have to vote to Remain in order to defend investment, defend jobs, defend workers' rights and defend our environment," Corbyn said.
The EU referendum is still on knife-edge and both sides have acknowledged that Labour supporters' votes will count.
Corbyn appealed to the 9.3m people who voted for Labour in the 2015 General Election to back Remain, stating jobs and workers' rights are dependent on Europe.
In just his second speech on the EU, Corbyn added: "We face enormous challenges of climate change, cyber crime, the power of global corporations to try and evade taxes. We need to have a strong message that we can stand up to defend workers' rights and deal with the huge challenges of global refugee movements and protect the freedom of people in Britain to live, work and retire abroad.
"I am supporting the Remain campaign in order to try and improve workers' rights and stand up to global corporations.
"We also have to look at our own industries. The Tory government has only reluctantly and latterly decided there is some merit in defending and supporting our steel industry. They're still trying to block EU moves to defend the European steel industry against Chinese dumping.
"Our campaign will be to Remain but it will also be settling out a stall of what we want in the future. We want to protect workers' rights we've achieved, we want to stand up for the rights of people all across this continent on a human rights agenda and above all we want to defend the environment across Europe. We see it as an act of solidarity. Going it alone won't help them and it won't help us."
Corbyn also added that a Labour government in Europe from 2020 would protect the UK from the Transatlantic Trade and Investment Partnership.
Alan Johnson, who is leading Labour's In campaign also said that Labour In's bus would be his home for the next six weeks as he makes the argument for continued membership of Europe. He added that the Labour party is focussed on the EU referendum.
"Every resource of the Labour party will be put into this campaign to get a Remain vote," he said.
The news comes after a raft of new polling, the majority of which puts Remain ahead. A poll by the British Chambers of Commerce yesterday showed support among business for Brexit growing, though Remain still commands a steady lead.