Asked what that should be, he indicated a much more radical Left-wing agenda than Sir Keir.

“Put more things back under stronger public control – energy, housing, water, transport,” he said bluntly.

He pointed to his actions on buses in Greater Manchester, saying he was the “first to do it” and had helped make it more affordable with £2 fares.

He railed against former Tory prime minister Margaret Thatcher for deregulating Manchester’s buses, saying “they just worked for private shareholders and not the paying public”.

He added: “You take that principle and you apply it to energy, you apply it to water – that’s what we need to do.

“The country gave away its control of the basic things people depend upon every day and that was a big mistake in my view.”

Mr Burnham, who has become hugely popular in Manchester during his mayoralty, has also previously said he wants to see a reversal of Brexit.

He told The Guardian last year: “Long term, I’m going to say it, I want to rejoin. I hope in my lifetime I see this country rejoin the European Union.”

But his longstanding pro-EU stance could prove deeply controversial in a Brexit-backing constituency, where Reform UK is expected to throw everything at the by-election.