John McDonnell has signalled that Labour is moving closer to backing a second public vote on Brexit.
The shadow chancellor said Labour had kept the option on the table and "we're moving towards that".
His comments come with Labour deeply divided over the issue which was partly responsible for the breakaway Independent Group of MPs quitting the party.
Britain'sShadow Chancellor of the Exchequer John McDonnell speaks during the Labour Party's annual conference at the Arena and Convention Centre (ACC), in Liverpool, England, Monday, Sept. 24, 2018. Britain's main opposition party took a step at its annual conference toward backing a new referendum on Brexit — but stopped short of saying the vote should include an option not to leave the European Union at all. (Peter Byrne/PA via AP)
Britain's main opposition Labour Party leader Jeremy Corbyn, foreground, and Shadow Chancellor of the Exchequer John McDonnell, left, during the Labour Party's annual conference in Liverpool, England, Monday Sept.24, 2018. Delegates at the party's annual conference in Liverpool will consider party policies. (Peter Byrne/PA via AP)
MP John McDonnell, Shadow Chancellor speaks ahead of the Grenfell fire one year anniversary solidarity march organised by Justice4Grenfell and the Fire Brigade's Union, in Westminster in London, Saturday, June 16, 2018. A year ago, London's Grenfell Tower high-rise was destroyed by a fire that killed 72 people. It was Britain's greatest loss of life by fire since World War II. (AP Photo/Kirsty Wigglesworth)
Britain's Labour Party leader Jeremy Corbyn, centre, and shadow Chancellor of the Exchequer, John McDonnell, attend a rally in Brighton, southern England, ahead of Labour Party's annual conference, Saturday Sept. 23, 2017. (Stefan Rousseau/PA via AP)
From left to right politician John McDonnell, Leader of Britain's Labour Party, Jeremy Corbyn, director Ken Loach and screenwriter Paul Laverty, pose for photographers upon arrival at the premiere of the film 'I, Daniel Blake', at a central London, Tuesday, Oct. 18, 2016. (Photo by Joel Ryan/Invision/AP)
John McDonnell, British Labour MP, speaks to the media outside the Palace of Westminster, Friday July 14, 2006 to announce his challenge for the Party Leadership. The leftist Labour Party legislator on Friday declared his candidacy to succeed Prime Minister Tony Blair, calling for the party to take a turn to the left. John McDonnell, 54, chairman of the Socialist Campaign Group, said he saw no difference between Blair's policies and those of Treasury Chief Gordon Brown, who is expected to become the party's next leader. (AP photo/Alastair Grant)
Shadow Chancellor John McDonnell speaks with the media during an event at the Millennium Hotel in Glasgow, where he pledged to deliver the "biggest transfer in wealth and power" from London to Scotland for more than seven decades if Labour wins power in the next general election.
Shadow chancellor John McDonnell makes a speech at Savoy Place in London where he shows his scars after a fall.
Jeremy Corbyn, with members of the shadow cabinet including Diane Abbott, Richard Burgon, Emily Thornbury, Rebecca Long-Bailey, John McDonnell and Keir Starmer, arriving for his speech during the Labour Party annual conference at the Arena and Convention Centre (ACC), in Liverpool. Picture date: Wednesday September 26th, 2018. Photo credit should read: Matt Crossick/ EMPICS Entertainment.
A Labour supporter wears a T-shirt bearing the face of Shadow Chancellor John McDonnell during an event in the University of Bradford to launch the party's manifesto
A Labour supporter takes a selfie with John McDonnell ahead of Jeremy Corbyn's first keynote in Westminster to begin the election campaign ahead of the snap election announced this week by PM Theresa May on June 8. Picture dated: Thursday April 20, 2017. Photo credit should read: Isabel Infantes / EMPICS Entertainment.
Shadow chancellor John McDonnell MP salutes as he sings The Red Flag, after Jeremy Corbyn's speech on the fourth day of the Labour Party conference in Liverpool. Picture date: Wednesday September 28, 2016. Photo credit should read: Matt Crossick/ EMPICS Entertainment.
Shadow Chancellor of the Exchequer John McDonnell visits Make Liverpool, an open access business unit that allows small start up companies to rent space and use equipment to help their businesses grow.
Shadow chancellor John McDonnell joins members of London's LGBTI community, as they hold a vigil in Old Compton Street, Soho, in solidarity with the people of Orlando, after the shooting there in a gay nightclub, Pulse, in the early hours of Sunday morning.
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Labour's position, thrashed out at the party's conference last year, keeps open the option of a so-called People's Vote if Theresa May is unable to get a deal through Parliament and there is not a general election.
Mr McDonnell told the Evening Standard: "On the People's Vote, we've kept it on the table and we're moving towards that."
He said Labour was "moving into implementation stages around our conference decision, around the People's Vote".
A compromise plan put forward by Labour MPs Peter Kyle and Phil Wilson could present a route to the party supporting a vote.
The two MPs have devised a plan to support the Prime Minister's Brexit deal on the condition it is put to a confirmatory public vote.
The Commons could be asked to vote on the Kyle-Wilson amendment next week.
Mr McDonnell said that any referendum would have remaining in the European Union as the alternative to the deal.
"If we were going on a People's Vote based on a deal that has gone through Parliament in some form, if that got voted down then you'd have status quo, and that would be Remain," he said.
The shadow chancellor said that if it was an option "I'd campaign for Remain and I'd vote for Remain".
A spokesman for the People's Vote campaign said: "It looks like Labour will test whether its Brexit plan has the support of Parliament next week.
"It deserves scrutiny but, with the Prime Minister effectively ruling out a customs union, John McDonnell and other senior Labour figures recognise there will be only one option left for them which is in line with party policy.
"If they back compromise proposals to put any final Brexit deal to the people, it will help unite their party, as well as avoid the catastrophe for their constituents of a no-deal departure from the EU."
Meanwhile, Jeremy Corbyn was setting out his Brexit plans in Madrid at the Party of European Socialists meeting.
Mr Corbyn said: "The damaging deadlock on Brexit must be broken and following my discussions with European Union leaders and officials, I am in no doubt that Labour's alternative plan is credible and could be negotiated with the EU."
He added: "None of us can allow Britain's exit from the European Union to be exploited by the whims of big business and the super-rich.
"Companies who shift their accounting operations back and forth across borders to minimise their tax bills are carrying out daylight robbery.
"By failing to crack down on aggressive tax avoidance, Theresa May is allowing the British public to be ripped off and exposing the kind of Brexit she and her party want to deliver."