Andy Burnham has said a future Labour government should reverse the 1p income tax cut and bring back the 45p rate, in a challenge to party leader Sir Keir Starmer.
The Labour mayor said the plans, unveiled by the chancellor on Friday, are not targeted enough.
“I don’t think it’s a time for tax cuts, it’s a time to support people through this crisis,” he said.
His comments go further than members of the shadow cabinet, who have criticised the decision to cut the top rate for those earning more than £150,000.
Party sources also said it would not be appropriate to set out the party’s tax plans potentially two years from a general election.
The Greater Manchester mayor called the Conservative’s mini-budget a “flagrant act of vandalism on the social cohesion of this country”.
Speaking to Sky News’s Sophy Ridge On Sunday programme, he said: “You have a budget that splurges billions on the wealthiest people in the country and actually doesn’t do anything meaningful to get people through the autumn and the winter.
“So honestly, I can barely believe it. Having been through a period of national unity, the way I would describe it Friday’s budget was a flagrant act of vandalism on the social cohesion of this country.
“The Government has drawn battle lines with working people - they’ve told us which side they’re on.”
But shadow cabinet minister Ed Miliband rejected the call to reverse the 1p tax cut. “I don’t think we should reverse that tax cut,” he said, pointing to an analysis which showed those earning up to £155,000 would be worse off.
Prime minister Liz Truss has vowed to "usher in a decade of dynamism" as she defended the tax cuts amid criticism it disproportionately helps the rich.
Labour has accused the Prime Minister and Kwasi Kwarteng of a "trickle-down" they say will, leave the next generation worse off.
Ms Truss insisted she was "unapologetic" in "focusing relentlessly on economic growth", even as the £45 billion tax-slashing package sent the pound tumbling to fresh 37-year lows.
Andy Burnham also urged his party to back electoral reform as he said it is now "odds on" that the UK will have a Labour government within the next two years.
The party’s annual conference is being held in Liverpool this week.
