John McDonnell has said unlike Jeremy Corbyn he will not remain neutral in any second EU referendum.
The shadow chancellor said individual members of the party and the shadow cabinet will be able to campaign on the basis of their judgment.
Labour, he said, would “negotiate a sensible deal, put that back to the British people alongside Remain and people will have to make a judgment around that deal as against Remain”.
Asked whether he would stay neutral, he told Sky News’s Sophy Ridge on Sunday: “No, I won’t and I don’t think Jeremy’s asking people to do that.
“I’ll wait until I see the details of the deal that we negotiate.
“I’ve said up until now – I was in the negotiations with the Conservatives for six weeks and I couldn’t see a deal even emerging then that could beat Remain, but let’s see what we can negotiate.”
Jeremy Corbyn has defended his decision to remain “neutral” in any new EU poll, saying it is a sign of “strength and maturity”.
The Labour leader came under fire after disclosing he would not take sides in the proposed public vote on a new Brexit deal which the party intends to negotiate with Brussels.
McDonnell said he would not expect an independence referendum in Scotland in “the first two or three years” of a Labour government.
“We’ve got to address the priorities, the real issues facing our community.”
Asked if he would put money on Labour winning the election, he said: “I’ve given up on gambling.
“It was one of my new year resolutions. But we’re going to win.”
Asked if a future Labour government would take a position on the deal it would negotiate with Brussels or not, shadow education secretary Angela Rayner told BBC One’s The Andrew Marr Show: “Well, that’s a hypothetical.”
Rayner said her party will negotiate a deal that puts jobs and environment protections first and which will deal with the Northern Ireland border.
“I think some of the problems that we have at the moment is the framing of this is that everybody’s Remain, and that’s just not true,” she said.
“Actually the country did vote to leave the European Union, and we’ve said we respected that, so we’re not going to be like the Lib Dems and just ignore that.
“We will negotiate a deal and we’ll put that back to the people, and they will have the ultimate say, and then we’ll move on.”