Tom Watson has said Labour can not rule out backing a second referendum on EU membership.
The party’s deputy leader said on Sunday it was not “likely” that Labour would push for another vote.
But he told BBC Radio 5′s Pienaar’s Politics “when you are in complex negotiations on behalf the nation you shouldn’t rule anything out”.
“We have not said we want a second referendum. What we actually want is a negotiated settlement,” he added.
His comments came after a BMG poll for The Independent showed 51% of voters now backed remaining in the EU, while 41% wanted Brexit to continue.
In November, Shadow Home Secretary Diane Abbott told constituents she would “argue for the right of the electorate to vote on any deal that is finally agreed”.
Pressed on whether that meant she backed a second referendum, Abbott told the BBC’s Andrew Marr programme today she meant MPs should have a say - not voters.
“The Labour Party does not support a second referendum and we’ve never supported it and we don’t support it now,” she said. “We think the electorate should have a say via their elected representatives.”
Shadow International Trade Secretary Barry Gardiner, asked for a yes or no answer to whether Labour could back a second referendum, told Sky News: “The Labour Party has not said we will have second referendum. We will honor the referendum result.”
Conservative immigration Brandon Lewis MP said the comments “confirmed Labour’s approach to Brexit is a shambles. “They won’t rule out a second referendum and can’t say what their policy is on immigration or continuing to pay into the EU,” he said.
“Just as we have agreed a deal which means getting control of our laws, money and borders, Labour would take us back to square one.”
Lib Dem leader Vince Cable said Watson’s comments were “encouraging” and a “tacit acknowledgment that this is what the British public increasingly wants”.
“But the problem with the position of Jeremy Corbyn’s and John McDonnell’s Labour is that they keep saying they won’t rule things out - it’s about time they started ruling things in,” he said.
Questions over Labour’s precise Brexit position came as Theresa May looks set to avoid a humiliating second Commons defeat after a compromise deal was reached within Tory ranks over plans to write the Brexit date in law.
Behind-the-scenes efforts to prevent a revolt appear to have resulted in a situation which will see March 29 2019 written into the government’s Brexit legislation as the prime minister promised, but with flexibility allowing the date to be changed if negotiations with Brussels look set to stretch beyond that date.
Rebels who helped inflict May’s first Commons defeat on Wednesday lined up behind the compromise, which has been put forward by prominent backbenchers on both sides of the EU referendum divide.