Jeremy Corbyn has fallen into line with Labour MPs by agreeing to join the party’s campaign for Britain to stay in the European Union.

The Labour leader, who voted for the UK to leave the then European Economic Community in 1975, had warned he could back British exit if the Prime Minister watered down EU-wide workers’ rights.

The group is committed to campaigning for Britain to stay in the European Union no matter what Mr Cameron achieves as part of his re-negotiation (Getty)

However, the Prime Minister appears to have rejected calls from Conservative backbenchers to try to secure an opt-out from European employment law.

A pro-EU Labour group, led by the former Home Secretary Alan Johnson, is set to launch on 17 November. It is backed by 213 of Labour’s 231 MPs – including every member of the Shadow Cabinet.

The group is committed to campaigning for Britain to stay in the European Union no matter what Mr Cameron achieves as part of his re-negotiation.

Speaking to The Independent on Sunday, Mr Corbyn insisted he was “proud” to support Labour’s Britain In Europe campaign.