Sir Keir Starmer today denied Labour plans to tackle rising energy bills was simply "kicking the can down the road", describing its policies as "big, bold and fully costed".
The Labour leader defended his party's proposals for a six-month freeze on energy bills at the current £1,971 price cap, funded in part by expanding the windfall tax on oil and gas profits.
Answering listeners' questions on Radio 5 live, he said: "I think for the millions of people that won't be able to pay those bills, hearing the Labour party say we would freeze those bills, we would not let that happen and we will use money from a windfall tax on oil and gas companies, who have made much more money - much more than they were expecting - to pay for that, that's a huge relief.
"I don't accept that's kicking the can down the road."
Some experts and thinktanks have warned that such a plan would prove inadequate to the scale of the cost of living crisis, with one listener to Nicky Campbell's phone-in programme urging the Labour leader to be more radical.
On long-term plans, he said: "I accept the challenge that something has got to be done in April."
Starmer, who will turn 60 on Friday, said although he was not claiming "great poverty", he knew what it was like not to be able to pay bills, saying in his childhood he remembered the phone being cut off for "months at a time".
He also described himself as a "proud trade unionist", and said: "Nobody has been fired for going on a picket line." He stressed that the former shadow transport minister Sam Tarry had been sacked for doing media interviews he was not authorised to do and making policy "on the hoof".
Asked if it was permissible for a shadow minister to stand on a picket line, he said: "No, look, each case will be looked at as it comes along, that is what we have been doing in relation to these cases."
He added: "I completely understand what people are going through and I support the right to strike." It was simply a "question of roles". "I want to be the Labour prime minister. I don't think the role of the prime minister is to have a cabinet meeting and then go on to a picket line."
He denied one listener's claims that Starmer was moving away from Labour values in order to make the party more electable. "The arguments and policies we are putting forward are absolutely fundamental Labour values," he said. It was vital Labour transform itself after the 2019 election defeat, he added.
"We have lost four elections in a row and that means we have let working people down. I'm not going to let that happen again."
He added: "If you lose that badly, you put a mirror up, you look at the Labour party. It's not the electorate that has to change, it's the Labour party that has to change."
Related: It's time for Labour to show voters that it, not the Tories, can mend the economy | Ben Nunn
The UK needed to make Brexit a success, he said. "We are not going back to the EU. We've now left. We have got to make it work.
"We have got the protocol in place and we should build on that, not rip it up," he said.
"The government has said it is going to rip it up - that is what is destroying our reputation internationally."