Jeremy Corbyn has repeatedly refused to clarify whether he would back Remain or Leave in a Brexit referendum he would call as prime minister.
The Labour leader did not rule out remaining neutral in a referendum giving the public the option between a “credible” new exit deal he would negotiate and staying in the EU.
Senior shadow cabinet colleagues including John McDonnell, Tom Watson and Emily Thornberry have been vocal in saying they would back Remain, regardless of any deal secured by Labour.
And Welsh Labour further exposed the rift on Wednesday by saying they would campaign to stay in the EU, shortly after Mr Corbyn outlined his plans to offer a “sensible” Brexit option.
Mr Corbyn would not make clear which option he would prefer when asked repeatedly in an interview.
“My job as prime minister would be to deliver that option that’s chosen by the British people,” he said.
“I will credibly present the options and say ‘this is the option, you can Remain, possibly with some reforms to the European Union, or you can Leave, but you will be leaving on these terms which would protect jobs and living standards and trade’.”
Pressed if he would remain neutral in the campaign, Mr Corbyn said: “As prime minister I’m offering the people a choice – the only party that’s doing so.”
The Liberal Democrats have hardened their pro-Remain position, with leader Jo Swinson now vowing to revoke Article 50 immediately if her party won a general election.
Prime Minister Boris Johnson has taken the hardline approach of vowing to force Brexit through by the October 31 deadline, regardless of whether a deal is in place or not.
Mr Corbyn’s signalling that he could take a neutral position in a referendum campaign came days ahead of his party conference, where he is expected to come under pressure to take a stronger Remain stance.
During the interview, Mr Corbyn said he would win the support of his unequivocally Remain-backing colleagues going forward.
“I’ve shared these views with all of my colleagues in the party and I’m very confident they will come with me on this journey to make sure that the people of this country make the final decision,” he said.
Mr Corbyn wants to negotiate a deal with Brussels that would include a new customs union with the EU, a close single market relationship and guarantees of workers’ rights and environmental protections.
Meanwhile on Wednesday, First Minister of Wales Mark Drakeford wrote to members saying Welsh Labour “must and will campaign to remain in the EU”.
Mr Drakeford said: “Any type of Brexit, even the softest possible, will cause potentially irreparable damage to Wales and its economy.”
The Lib Dems were critical of Mr Corbyn’s stance, with Brexit spokesman Tom Brake saying: “Labour will never be a party for Remainers. Meanwhile, Liberal Democrats will continue to fight tooth and nail to stop Brexit.”