Jeremy Corbyn has said it is "not a matter" for the British Parliament to block another referendum on Scotland's independence.
The Labor leader said he "does not support" Scotland breaking out of Britain, but added that Westminster MPs should not prevent re-election.
Labor's Shadow Chancellor John McDonnell recently said the party would not block a Scottish independence vote, leading to a furious backlash by Scottish Labor leader Richard Leonard.
When asked if he agreed with Mr McDonnell's statements on Thursday, Mr Corbyn replied: 'It is not up to Parliament to block them, but it is up to Parliament to decide whether or not it is a good idea ,
"I do not think it's a good idea."
Mr Corbyn, who called on rival parties to appoint him temporary prime minister, also failed to confirm on request whether a future Labor government would try to block a second independence vote.
"I would advise that we have no further referendum, I am not for the independence of Scotland," he added.
"What I support is justice for Scotland, and that means a Labor government invests in Scotland across the UK."
Regarding the 2014 poll, where "no" won by 55% -45%, the Labor leader added: "The referendum has taken place and a decision has been made.
"The best thing a Labor government would have is to make sure that Scotland receives the investment it needs, the social justice it needs, and the employment opportunities for young people who have been rejected."
Mr Corbyn's comments were welcomed by Scottish First Minister Nicola Sturgeon, who has already promised to hold another independence referendum before the end of the current legislature in Scotland in May 2021.
She wrote on Twitter: "I'm not Jeremy Corbyn's biggest fan, but he's right about that.
"It is legitimate to oppose independence and argue against a referendum – it is not legitimate for Westminster to block a democratic mandate and majority vote in @scotparl for # indyref2."
Commenting on what Mr Corbyn said, a spokesman for the Scottish Labor Party said: "Jeremy Corbyn and Richard Leonard have made it clear that there is no economic justification for independence, especially given the SNP's new position to drop the pound and one new policy of turbo-charged austerity measures to accept the deficit.
"What Scotland needs is a radical reform of the Labor governments in Holyrood and Westminster."
Scottish Conservative Deputy Chairman Jackson Carlaw accused Corbyn of "having surrendered to a second referendum on independence".
He said, "Both he and John McDonnell are preparing to hand over the referendum to Nicola Sturgeon in exchange for SNP support for a Labor government.
"Scottish Labor got stuck in the breeze – they do not even matter to their own party."
Scottish Liberal Democrat leader Willie Rennie said, "I'm sorry for the voters of the Scottish Labor Party.
"They have been hung over and over by a drying guide that makes it wrong in terms of independence and Brexit."
Legally, the Scottish Government can only hold an official referendum if the UK Government grants it the powers under section 30 of the Scotland Act.
Prime Minister Boris Johnson said there was "no reason" for the Scottish people to retune, and that the 2014 election was a "historic" and "once in a generation" vote.