Keir Starmer will reverse a £10,000-a-year Tory tax cut for the 660,000 highest earners in Britain if he gets into Downing Street.
The Labour leader said he will undo Friday's decision to get rid of the 45p top tax rate on earnings above £150,000 a year.
The move, set to deprive the Treasury of £2bn a year, will save 660,000 high earners an average of £10,000 a year each.
Until this morning, Sir Keir and his allies were refusing to say they would definitely bring back the 45p rate once they got into power.
But after pressure on the party, Labour's leader said: "I would reverse the decision they made on Friday.” He told the BBC's Sunday with Laura Kuenssberg: "It’s hugely risky, it’s hugely divisive and I would reverse it."
Sir Keir said he would keep the Tory decision to cut the basic rate of income tax by 1p in the pound, from 20p to 19p.
But asked if he'd bring back the 45p top rate, he said: “Yes.
"I do not think that the choice to have tax cuts for those that are earnings hundreds of thousands of pounds is the right choice when our economy is struggling the way it is, working people are struggling the way they are, and public services are on their knees.
"That is the wrong choice."
In an interview kicking off Labour's conference in Liverpool, Keir Starmer refused to pledge public sector wages would rise with inflation - currently around 10%.
Instead, he said he would change the rules of the Low Pay Commission to set the living wage not just by reference to the median wage, but also to the cost of living.
That would “lock in for the long term and increase in the living wage that takes account of the cost of living”, he said. He added: “It’s not for me to wade in and say it should be this amount or that amount”.
Keir Starmer also refused to extend his current offer to freeze household energy bills for six months - compared to the Tory pledge of two years.
Labour’s leader said it was “wrong” for the Tories to simply make the pledge based on tens of billions in borrowing, rather than costing it properly and pledging a windfall tax.
He also dodged questions on whether he backed workers going on strike when they get a real-terms pay cut.
Instead he said: “When people go on strike it is a last resort at the end of negotiations and I can quite understand how people are driven to that.”
It's reported Liz Truss is drawing up a new round of tax cuts in the new year - from annual allowances on pension pots to a £5,000 tax break for earners on more than £100k.
Today the Prime Minister vowed to "usher in a decade of dynamism" and Chancellor Kwasi Kwarteng said their tax cuts were just the "first step towards igniting growth”.
In a speech to activists last night, Sir Keir said the Chancellor's admission of Tory economic failure would be hung "around their necks" in the next election campaign.
"If you earn a million pounds, yesterday, you got a £55,000 tax cut, enough to pay for a nurse," he told activists in Liverpool.
"It's not trickle down, it's taking the p***.”
TUC general secretary Frances O'Grady told the BBC: "This is the economics of Narnia."
And Greater Manchester mayor Andy Burnham said Friday’s Budget was a “flagrant act of vandalism on the social cohesion of this country”.
He told Sky News’ Sophy Ridge on Sunday: “Borrowing billions of pounds for bankers and billionaires - it’s just obscene.”
This breaking news story is being updated.