Union boss Mick Lynch has called on Keir Starmer to show he really understands what struggling Brits are going through by showing more passion - but said he isn't calling for him to sacked.
The RMT leader today told The Mirror that the Tories under Liz Truss have already put forward a "radical" agenda to benefit their supporters, and urged Labour to do the same.
He added that rail companies and the government are not making "any bold steps" to prevent rail strikes which threaten to disrupt next week's Tory Party Conference in Birmingham.
Referring to Chancellor Kwasi Kwarteng's budget last week, which overwhelmingly benefitted high earners, Mr Lynch said: "We've seen how radical the Tories are being for the benefit of their people, we need Labour to be equally radical for the benefit of working class people."
Speaking after a Transport Fringe event at the Labour Party Conference in Liverpool, Mr Lynch urged the Labour leadership to stop being cautious - but clarified that he will not at any point be calling for Mr Starmer to go.
He rubbished rumours circulating today that he had called on the party leader - who this morning vowed to undo a Tory tax cut benefitting the UK's 660,000 highest earners - to resign.
"Working people need to be able to say that Keir Starmer and (shadow Chancellor) Rachel Reeves really get it," he said.
"I'd like to hear a passionate outpouring from him to show he knows what people are going through.
"If he can't do that then he needs to think about getting out the way. But I want to be clear, I want him to win the next election, I want him to be the next Prime Minister and I want Labour to be the party in power."
Public ownership of transport networks and building council houses are among the central issues Labour should be championing, the union boss - who is not a member of the party himself - said.
Thousands of RMT members are set to walk out next Saturday in a strike co-ordinated to disrupt the Tory Party conference, and Mr Lynch said there would be talks going on through the week.
"The timing isn't an accident, we need to keep the strikes going and we need to make sure they're effective, it's a perfectly legitimate thing to do when there's an important conference run by the governing party, I make no apology for that."
Although discussions are still being held, he said: "They're not making any bold steps to get the strikes called off next week."
At a lively fringe meeting he called for party members to stick together - although angry audience members voiced opposition to Mr Starmer's leadership.
He said: ."We will not be divided from our friends in the Labour Party, we're here because of the Labour Party members are part of our DNA," he said. Nevertheless he added: "We've got to keep the top pressure under pressure, not just on transport but on every issue. We will work with anyone who has progressive ideas and we've got the right to criticise, and I think many more trade unions should have that relationship."
During the meeting pensioner Audrey White - who was expelled from the Labour Party after confronting Mr Starmer when he visited the city earlier this year - fumed: "I don't think they'll ever let a real socialist into the leadership. We've got to have radical change."
Mr Lynch - who was mobbed for photos when the discussion drew to a close - launched a blistering attack on former Transport Secretary Grant Shapps, branding him a "hologram", who is now "fondling his flag" in his Welwyn Garden City constituency after being sacked.
He criticised the former cabinet member for his failure to meet unions in an effort to prevent a wave of strikes, saying: "I think he's some kind of hologram, if he actually exists."
The RMT boss said his first meeting with Mr Shapps's successor Anne-Marie Trevelyan had been a "good meeting with a positive attitude".
