Keir Starmer has refused to give his backing to 11 left-wing Labour MPs standing at the next election.
The Labour leader repeatedly dodged the question when asked to endorse the backbenchers, who last month signed a Stop The War Coalition letter on the crisis in Ukraine.
They included former shadow cabinet members John McDonnell, Diane Abbott and Richard Burgon.
The letter criticised Nato expansionism as a contributory factor to Russia’s decision to invade Ukraine.
After being warned they faced disciplinary action by Labour’s chief whip, all 11 removed their names from the letter.
Asked on BBC Radio 4′s World At One whether he supported the MPs standing for Labour at the next election, Starmer twice avoided the question.
After being asked a third time, he said: “They are Labour MPs and of course I support them but all of our MPs will go through a process for selection into the next election.”
Last month, the Labour leader told his MPs that any of them who drew “false equivalence” between the actions of Nato and Russia would be kicked out of the party.
He said: “Labour’s commitment to democracy, the rule of law and the sovereignty of independent nations is unshakable.
“Vladimir Putin is attacking all those things. Nato is defending them.”
HuffPost UK also revealed how John McDonnell, the former shadow chancellor, faced losing the Labour whip if he went ahead with a planned appearance at a Stop The war Coalition rally.
He eventually pulled out on the day of the event, saying: “This is not the time to be distracted by political arguments here. Now is the time to unite and do all we can to assist the people of Ukraine desperately seeking asylum and to do all we can to bring about peace.
“Nothing is more important at this time. Nothing should distract us from that. So I won’t feed into that distraction by going tonight.
“I do think many Labour Party members will want clarity over the Labour Party’s attitude to attending demonstrations organised by Stop The War or by them jointly with other groups.”