The wealthy will be willing to pay more tax if the money is spent on better public services, Jeremy Corbyn has insisted in a defence of his economic plans.
The veteran left-winger, who will launch a package of environmental policies in the latest stage of his Labour leadership campaign, rejected the claim by critics he was a "deficit denier" but insisted that cutting services and benefits was not the best way to balance the books.
Meanwhile leadership rival Yvette Cooper turned her fire on David Cameron, insisting the battle within Labour should not allow the Prime Minister to get away with the "lies" he has told the electorate.
Mr Corbyn, whose momentum showed no sign of slowing at a packed campaign event in Norwich, said he wants to lead a "more inclusive and united party" after the bitter leadership race has finished on September 12.
Writing in the Independent, he tackled some of the charges levelled against him by critics of the anti-austerity message which has established him as the frontrunner in the campaign in terms of declared support, although Andy Burnham remains the bookmakers' favourite.
In a marked contrast to the New Labour philosophy, Mr Corbyn stressed he was "absolutely not relaxed about a few people being filthy rich while others are destitute".
The Islington North MP said: "I detest inequality and injustice. We should not ignore the exploitation of workers, the degradation of our environment - or tax dodging by multinationals, which creates an unfair advantage over local businesses.
"Demanding tax justice is actually a moderate pro-business campaign: it seeks a level playing field for all.
"Many well-off people I speak to, in Islington and around the country, would be quite happy to pay more tax to fund better public services or to pay down our debts.
"Opinion polls bear this out: better off people are no less likely to support higher taxes. A more equal society is better for us all. "
Although Mr Corbyn acknowledged the deficit must be tackled, if the books had not been balanced by 2020 he would not, as a potential Labour prime minister, set an "arbitrary deadline" to get Britain back in the black.
He rejected the suggestion he was "unelectable", highlighting his eight election wins in Islington North, although the constituency is a safe Labour seat.
His plan for success on the more challenging national battleground is to tackle apathy through "straight-talking politics".
"If we had won the support of just one in five of those who didn't vote, then today we might have a Labour government," he said.
"I think an honest, straight-talking politics can win back support from the Conservatives, Ukip, the Greens and SNP."
Shadow home secretary Ms Cooper used an interview in the Guardian to warn that Labour must not let its internal conflict distract from the task of opposition.
She said: "We may have our own leadership election going on, but Labour can't allow David Cameron to get away with this and carry on like nothing has happened - he is taking the British public for fools."
Ms Cooper pointed to measures on child tax credits, housing and rail electrification as evidence the Tory leader had gone back on pre-election promises.
She said: "We have to confront him directly on every lie and broken promise - that's exactly what I plan to do in parliament and across the country.
"It's time the Prime Minister and George Osborne were held to account for deceiving people and letting them down."
The process for vetting supporters signing up to pay £3 to take part in the leadership election has come under further scrutiny amid claims that hard-left groups were attempting to take part in the contest.
The Times reported that 11 people who stood as candidates for the Trade Unionist and Socialist Coalition in the general election had managed to sign up without being caught by the vetting process.