Labour's new leader Jeremy Corbyn will not rule out backing Britain leaving the European Union, Chuka Umunna has claimed.

After refusing to resign, Mr Umunna was ousted from his role as shadow business secretary by Mr Corbyn after the pair clashed on key policy areas.

In a damning statement he revealed how the hardline leftwinger wants to leave open the possibility of joining the campaign to sever ties with Brussels.

Chuka Umunna has claimed new Labour leader Jeremy Corbyn made clear he wanted to leave the door open to Britain leaving the EU

In an attempt to repair the damage, shadow foreign secretary Hilary Benn today sought to claim that Labour would campaign to stay in the EU.

But the row lays bare the deep split over Europe and foreign policy which led to several senior figures refusing to serve under Mr Corbyn.

Mr Corbyn told the Parliamentary Labour Party today that Labour ‘can't just give (David) Cameron a blank cheque’ and any changes the Prime Minister secures ‘must be the right ones’.

Within hours of Mr Corbyn's extraordinary victory being announced, leadership rivals Yvette Cooper and Liz Kendall led a frontbench exodus, joined by Rachel Reeves, Tristram Hunt, Emma Reynolds and Chris Leslie.

Mr Ummuna was widely reported to have joined them, after declaring in July that Mr Corbyn was 'unelectable' and said he would not be able to serve in his shadow cabinet.

However, Mr Umunna is refused to quit and waited to hear from the leader's office. Friends said: 'As far as we are concerned he is in the shadow cabinet until he is sacked.'

The sacking came last night after a face-to-face meeting between the two men ended without without finding common ground.

Mr Umunna said there were 'differences, not least on the European referendum' and he would find it 'difficult to abide by the collective responsibility that comes with serving in the Shadow Cabinet'.

And in a damning revelation he added: 'I cannot envisage any circumstances where I would be campaigning alongside those who would argue for us to leave – Jeremy has made it clear to me that he does not wholeheartedly share this view.'

Jeremy Corbyn, pictured leaving his London home this morning, is facing increasing pressure from Labour MPs over his foreign policy stances

David Cameron has promised to renegotiate Britain's members of the EU before staging an in-out referendum by the end of 2017.

WITHIN HOURS, HIS FIRST U-TURNS Just hours after becoming Labour leader, Jeremy Corbyn has been forced to announce his first U-turns. After three decades of campaigning for Britain's exit from Nato, allies said tonight he would no longer push this policy, or advocate withdrawal from the EU, despite having questioned Britain's membership for years. It also emerged that he might accept a place on Her Majesty's Privy Council – even though as a republican he has always said he would turn it down. But Diane Abbott, a hard-Left ally, said he remained opposed to the renewal of Trident. She said the apparent changes of tack were 'red herrings' after deputy leader Tom Watson conceded there were differences on key foreign policy issues that would require compromises if the party was to unite behind the new regime. Mr Watson – whose role is seen as a crucial to secure party unity – accepted that he and many other MPs opposed Mr Corbyn over the renewal of Trident. But he told the BBC's Andrew Marr Show that the party could present a united front on Nato and membership of the EU, adding: 'These things have got to be worked out.' Miss Abbott told BBC Radio 4's The World This Weekend: 'I can say with confidence Jeremy is not taking us out of Nato and he is not taking us out of the EU, those are red herrings.' Advertisement

The other Labour leadership contenders - Andy Burnham, Liz Kendall and Yvette Cooper - all argued that Brussels needs reform but would always vote to stay in.

But Mr Corbyn has repeatedly dodged questions on the issue, raising the spectre of a return to Labour's Euroscepticism of the 1980s.

On the eve of his landslide victory, he revealed how he backed Britain leaving the European Community in a referendum in 1975.

Voters were asked: 'Do you think the United Kingdom should stay in the European Community (Common Market)?' In the final result, 67 per cent of people voted to remain.

Asked at a campaign rally in North London how he voted in the 1975 referendum, Mr Corbyn told Reuters: 'I did vote and I voted 'No'.'

However, in an interview this morning Mr Benn sought to reassure pro-Europeans in the Labour party.

He told BBC Radio 4's Today programme: 'Jeremy said, whatever differences we may have with some aspects of European policy, whatever reforms we want to see, we will stay to fight together for a better Europe. It's absolutely clear.'

Asked to confirm that this would be the case regardless of the renegotiation being undertaken by the Prime Minister, he said: 'Under all circumstances.'

A number of senior Labour for benches quit in part in protest at Mr Corbyn's stance on Europe.

Shadow communities secretary Emma Reynolds, writing for website Progress this week, said: 'The referendum on Britain's membership of the European Union will be the defining political event of this parliament. The outcome will determine the future of our country and place in the world.

'So this is not an issue that the Labour party or its new leadership can duck or fudge. As internationalists who believe in solidarity and collectivism, we should campaign unequivocally to remain a member.'

Mr Umunna was seen as a frontrunner to become Labour leader until he quit the race days after launching his campaign in May.

He was tipped to become shadow foreign secretary if Andy Burnham or Yvette Cooper won, but both were trounced by Mr Corbyn.

In the first round, Mr Corbyn won 59.5 per cent of the vote - 251,417 of the 422,664 votes cast - against 19 per cent for Mr Burnham, 17 per cent for Ms Cooper and just 4.5 per cent for Ms Kendall.

In an attempt to repair the damage, shadow foreign secretary Hilary Benn today sought to claim that Labour would campaign to stay in the EU

Last night Mr Umunna said: 'If Jeremy's clear victory yesterday demonstrated anything, it was a desire for politicians to be true to what they believe – I want to abide by this.

'Also, Jeremy should be free to appoint a Shadow Cabinet committed to implementing the policies on which he campaigned in the contest – I clearly had some differences in view on how we build a more equal, democratic, free and fair society.'

Two weeks ago Mr Umunna appeared to open the door to serving in Mr Corbyn's team as he urged the party to unite behind whoever became leader.

He appealed for 'solidarity' and insisted the party must 'accept the result of our contest when it comes'.

Listing his misgivings about Mr Corbyn's policies, he said it was important for the party to maintain its pro-European stance, adding he had 'grave concerns' about increasing national insurance for middle income families by 7 per cent.

He said he was concerned about Britain withdrawing from Nato, adding: 'I don't think you can go around nationalising things without compensation, when we often invest in these things in our pension funds.'