Labour will contemplate a second referendum on Brexit if it cannot force a General Election, according to John McDonnell.
Speaking to ITV News, the shadow chancellor said the party would move "towards that consideration" if necessary.
Mr McDonnell, a close ally of Jeremy Corbyn, said Labour's preferred option remained a General Election if the government is defeated in the "meaningful vote" on Withdrawal Agreement on December 11.
However, he acknowledged that, under the fixed-term Parliaments Act, it could be difficult to achieve in which case Labour would back calls for a new "people's vote".
"I have not given up on the prospect of a General Election," Mr McDonnell told ITV News
"If we can't get a General Election, yes, we'll be moving towards that consideration of another referendum."
Asked whether Labour would back a remain vote, Mr McDonnell said that decision would be decided democratically.
"That will be decided democratically by our party," he said.
"We've campaigned for remain before, I've voted for remain and that will be the debate that we have.
"I voted remain last time, I'd vote remain again."
While Labour did formally support a second referendum in the absence of a general election at the party's annual conference in September, Mr Corbyn and other senior figures have previously appeared reluctant to embrace the prospect.
Asked if a warning by shadow home secretary Diane Abbott that a second vote could result in another victory for Leave, Mr McDonnell acknowledged that could be the outcome.
Speaking to the BBC, he said: "It's very difficult to call, it could go either way."
He added: "On the current deal, we couldn’t support the current deal, we couldn’t support that.
"As time moves on, we think we can build consensus around a compromise.
"If we can’t, well then the people decide."