Ex-Greek chancellor Yanis Varoufakis issued a strong warning to Jeremy Corbyn on Friday, advising the new Labour leader to move on from discussing his opposition to austerity.
Admitting that he was "in conversation with the Corbynistas", Varoufakis made the intervention amid a furore raging among Labour MPs over seismic shifts in their party's economic policy.
"My advice is to shift away from the narrative of austerity - pro-austerity, anti-austerity - it is not an issue," he told the BBC's 'Daily Politics'.
"[George] Osborne tried a little bit of austerity - we Greeks are the champions of austerity. You tried it out here with a very small amount; it didn't work and Osborne stopped it."
Anti-austerity protester demonstrate in London
The former finance minister called on Labour to get a grip of its media image, commenting that poor coverage in the press was the result of left-winger Corbyn experiencing much the same shock win as Syriza.
"They need more time to get their act together," Varoufakis said. "They were just propelled in to the limelight - just like we were - very suddenly.
"They didn't even expect it themselves!"
But pressed by host Andrew Neil to disclose his musings on Labour's expected fortunes, Varoufakis said: "Until and unless the Left in this country manages to... bring into the Labour fold - and in to politics - all these youngsters who don't care about you, me, Corbyn, Cameron, I think Britain will have failed and the Labour Party will not have been revived."
In his inaugural party conference address, Corbyn hailed plans to sign more young people up to vote as one of Labour's "first big campaigns".
Speaking last month, the opposition leader announced: "From today, our Labour Party starts a nationwide campaign for all our members to work in every town and city, in every university as students start the new term, to stop the Tory gerrymander. To get people on the electoral register."