Sir Keir Starmer has said has said a second EU referendum must remain an option for Labour.
Speaking at the Fabian Society new year conference in London, Sir Keir said Labour stood by the commitment made at the party conference last year in Liverpool.
"That is a very important commitment. It's a commitment to you, our members and our movement. And it is one we will keep," he said.
It came as Sir John Major called for Theresa May to relegate herself to a Brexit "mediator" after her deal was overwhelmingly defeated in the Commons earlier this week.
