Labour faces a fresh row over its Brexit policy after a frontbencher took part in a rally calling for a second referendum.

Shadow sports minister Rosena Allin-Khan said it was “time to take the Brexit decision back to the people”.

She was rebuked by Jeremy Corbyn, who said he would prefer Labour MPs to be “concentrating solely” on defeating Theresa May’s Brexit plan on Tuesday.

He said he would be discussing the situation with Dr Allin-Khan.

Labour’s official policy is to call for a general election and, if that does not happen, to then keep all options open, including the possibility of a second referendum.

Tooting MP Dr Allin-Khan joined a cross-party line-up at the rally, organised by People’s Vote and Best for Britain.

Dr Allin-Khan said: “The promises made in 2016 are so far removed from the reality of the 585-page Withdrawal Agreement that it’s time to take the Brexit decision back to the people.”

But she was careful to say that the vote should only take place if there was not a general election.

“When this deal is voted down by Parliament, I want us to call for a general election the very next day and if that is rejected then we need a people’s vote.”

She added: “Do not let them tell you it is betraying the will of the people because the biggest betrayal is that of our children, our hospital patients, our much-valued NHS workforce.

“We have had two general elections in the last three years and nobody is telling us that they were undemocratic.”

In an interview with ITV, Mr Corbyn said: “She’s entitled to her point of view. I would rather she and every other Labour MP spent today and tomorrow and Tuesday concentrating solely on making sure we defeat this deal and I would urge everyone else in the Labour Party to do that.”

Asked if she could remain on the frontbench he replied: “I’ll have a discussion with her.”

Mr Corbyn did not rule out Labour eventually supporting a referendum.

“All other options should be on the table, including the possibility of a popular vote, a referendum, later down the line,” he said.

The broadcaster reported that he had not ruled out Remain being an option on the ballot paper in another vote, although he stressed it could not be a “re-run” of the 2016 referendum, as this would be “met with a lot of dismay from a lot of people”.

The issue of a second referendum is highly sensitive for Labour, which fears losing voters in Leave-supporting areas.

Shadow cabinet office minister Jon Trickett said: “I think if people feel that a privileged political elite has decided by subterfuge to find a way of reversing the previous referendum, that would cause us some difficulty and rightly so.”

He told Sky News that for a referendum to take place “we need to show to the country that we’ve been through the various different options and if at some point a referendum becomes absolutely necessary, it’s at that point that it takes place”.

Mr Trickett said organising and passing legislation for a vote might take until May or June next year – after the UK’s intended departure from the EU on March 29, 2019.

Meanwhile, Labour will work with other parties to decide whether to attempt to oust Theresa May if her Brexit deal fails.

Mr Corbyn’s party could either attempt to force a general election or seek to form a minority government following a defeat for Mrs May on Tuesday, according to shadow cabinet ministers.

Senior party figures would not be drawn on whether Labour would table a motion of no-confidence in the Government immediately after the vote, indicating they would wait and see what happens in the aftermath of a Government defeat on such a defining policy issue.

Shadow business secretary Rebecca Long-Bailey said: “We’ll have to make an assessment at the time and we will be in discussions with other political parties across the House to assess what’s the best thing to do.”

She told BBC’s Andrew Marr Show: “Once the deal falls, the Prime Minister is under a duty then to set out what she is going to do next.

“What we would urge her to do is either call a general election – because she wouldn’t have the confidence of Parliament to carry on as Prime Minister and when a Government that can’t pass a key policy proposal such as this, I question their legitimacy to carry on.

“But alternatively she could offer to renegotiate around a deal that would provide consensus in Parliament and we have been trying to set out such a deal for some time.”

Mr Trickett told Sky’s Sophy Ridge on Sunday: “Our preferred option, very, very strongly, is that we refresh the Parliament though we are ready to form a minority government should that be necessary – and it could happen on Wednesday morning – and to begin to reset the negotiation and take the country forward in a much better direction.”