Sir Keir Starmer has accused the government of “gambling the mortgages and finances” of the British people with its “casino economics”.

Speaking before his party’s conference in Liverpool, the Labour leader tweeted: “Tory casino economics is gambling the mortgages and finances of every family in the country. Labour will secure growth for working people, that benefits all communities. My government will deliver a fairer, greener future.”

The chancellor, Kwasi Kwarteng, announced his fiscal aspirations in a £45bn tax-cutting package that will benefit the richest 1% at the expense of struggling households.

The announcement sent the pound crashing to its lowest level against the dollar in 37 years.

Announcing his mini-budget on Friday, he said economic policy should focus entirely on growth.

But Labour’s deputy leader, Angela Rayner, said the next generation would be left worse off after the government’s “trickle-down” approach to economics.

“We’ve had 12 years of the Conservatives and growth hasn’t expanded, and people haven’t seen that economy growing in a way we need it to,” she told BBC Breakfast.

“We’ve seen trickle-down economics before. It doesn’t work, we don’t believe it’ll stimulate the economy. And I think it will make the next generation worse off.”

Labour’s deputy leader said her party’s plan for growth would be different, adding: “We wouldn’t be making choices around the tax cuts at the moment, we don’t think that’s the way forward.”

“We would be asking the oil and gas companies to pay a little bit more when they’ve made billions of pounds of profits, instead of putting it all on the national debt. We don’t think that’s the right priority.”

Rayner hinted Labour would reverse the government’s income tax cut in an attempt to boost sustainable growth and ease the cost of living crisis for those on the lowest wages.

“We’ve said the income tax cut is the wrong priority. We don’t think that’s a priority,” she told BBC Radio 4’s Today programme.

“We will set out our tax proposals which will guarantee that those on the lowest wages, their cost of living will improve. We will have sustainable growth in the future. We will invest in high-skilled jobs and renewables, so we’re self-reliant on our energy needs.”

The Institute for Fiscal Studies said the only people to benefit from the tax cuts in the coming years would be those who earn over £150,000 while the rest would be left worse off.

“Well, if looked straightforwardly at people’s incomes with these tax changes, the more money you have, the more you gain,” the IFS director, Paul Johnson, told BBC Breakfast.

“In fact, because there was one big tax increase the chancellor didn’t reverse, and that is the fall over time in the point at which you start paying income tax. If you take that into account, in three or four years’ time, the only people gaining from this will be earning more than about £150,000 a year.

“If you’ve got less than about £150,000 a year coming in, if you’re part of the 99% with less than £150,000 coming in, then you’re still going to be worse off as a result of tax changes coming in over the next two or three years.”

The government has defended criticism of the chancellor’s mini-budget insisting it was “not a gamble but a necessity”.

“We can’t continue having high taxes, we can’t accept lower growth than we would like because the people in this country want higher wages,” the chief secretary to the Treasury, Chris Philp, told Times Radio.

“They want better standards of living, they want to see money invested in public services, they want to see investment, they want to see their children having a better future than they do.”

The only way to deliver those aspirations was through a growth plan, he added.