Chancellor Kwasi Kwarteng's mini-budget of sweeping tax cuts would "reward the already wealthy" and not boost economic growth, Labour has said.
Shadow Chancellor Rachel Reeves said the plan was a Tory "admission of 12 years of economic failure".
The measures were funded by unnecessary borrowing instead of a windfall tax on oil and gas firms, she added.
Mr Kwarteng spent billions on policies he said would shake up the UK's finances and boost economic growth.
In a statement to Parliament, Mr Kwarteng abolished the top rate of income tax for the highest earners as he unveiled the biggest package of tax cuts for decades.
His announcements included scrapping a cap on bankers' bonuses, reversing a rise in National Insurance and cutting stamp duty tax - a property purchasing tax - for some buyers.
The Institute of Fiscal Studies said the richest 10% of households would gain the most from Mr Kwarteng's measures, which undo the tax rises introduced by his predecessor, Rishi Sunak.
Torsten Bell, the chief executive of the Resolution Foundation think tank, said those earning £1m annually will get a £55,000 tax cut next year.
As the UK faces a recession, rising interest rates and soaring energy bills, Ms Reeves said "the Conservatives are the cost-of-living crisis".
But Mr Kwarteng argued his economic vision will "turn the vicious cycle of stagnation into a virtuous cycle of growth".
The Liberal Democrats said the chancellor's plan was "a recipe for disaster that will leave families suffering from soaring prices while banks and oil and gas companies rake in huge profits".
The Scottish National Party said the Tory government was "robbing the poor to pay the rich" and its measures do not go far enough to help people on low incomes.
Mr Kwarteng told MPs he was fulfilling new Prime Minister Liz Truss's promise to run a "tax-cutting government".
"For too long in this country, we have indulged in a fight over redistribution. Now, we need to focus on growth, not just how we tax and spend," he said in his statement.
In her response, Ms Reeves congratulated the chancellor "on his comprehensive demolition" of the Conservative government's record of the past 12 years.
"Their record, their failure, their vicious circle of stagnation," she added.
Ms Reeves said borrowing was higher than it needed to be after the Bank of England raised interest rates and warned the UK may already be in recession. "This is casino economics - gambling the mortgages and finances of every family in the country to keep the Tory party happy," Ms Reeves said.
She criticised the chancellor for refusing to release an independent forecast of how his tax changes would impact the economy, as the government usually does when it delivers major financial statements.
But because Mr Kwarteng's statement was not technically a budget, he said he would release this forecast "in due course" before the end of the year.
Ms Reeves said without this forecast, the chancellor's statement was "a budget without figures, a menu without prices", asking what he had to hide.
She referenced a tweet by US President Joe Biden, saying he was right to be "sick and tired" of "tickle-down economics", which was a "discredited" theory that would not "unleash the wave of investment that we need".
She said: "The chancellor has made clear who his priorities are today - not a plan for growth, a plan to reward the already wealthy.
"A return to the trickle-down of the past, back to the future, not a brave new era."