Sir Keir Starmer has accused Boris Johnson of dithering over more help for households struggling as inflation hits a four-decade high.
The Labour leader, who is calling for a windfall tax on oil and gas companies to help consumers hit by soaring energy bills, said the PM "doesn't actually understand what working families are going through".
He suggested the government will eventually U-turn over windfall taxes and that every day he delayed doing so he was choosing "to let people struggle when they don't need to".
The two leaders clashed over the issue after official figures showed inflation climbing to a 40-year high of 9% in April as the energy price cap was hiked.
Sir Keir called on Mr Johnson to "stop the hokey-cokey" of speculation and back Labour's plan.
He added: "Whilst he dithers, British households are slapped with an extra £53m on their energy bills every single day.
"Meanwhile, every single day, North Sea oil and gas giants rake in £32m of unexpected profit.
"So many people are living through this nightmare and they feel totally abandoned by this government."
Sir Keir cited evidence that some business leaders and Tory MPs were now backing the windfall tax plan.
The PM hit back by saying that Labour's plans were "always and everywhere to raise taxes on businesses".
But he added: "Of course we will look at all the measures that we need to take to get people through to the other side but the only reason we can do that is because we took the tough decisions that were necessary during the pandemic."
Mr Johnson said of Labour: "Nothing could be more transparent from this exchange than their lust to raise taxes.
He added: "We don't relish it, we don't want to do it, of course we don't want to do it, we believe in jobs and we believe in investment and we believe in growth.
"As it happens, the oil companies concerned are on track to invest about £70bn into our economy over the next few years, they're already taxed at a rate of 40%."
Earlier, foreign secretary Liz Truss admitted that the UK was in a "very very difficult economic situation" and admitted that inflation was "extremely high".
But she cautioned that a one-off tax of the sort proposed by Labour on the likes of BP and Shell - who have seen profits soar as oil and gas prices shoot higher - could deter investment.
Labour's shadow chancellor Rachel Reeves told Sky News: "Inflation a 40-year high and yet still the government... are refusing to take the action that is needed to help some of the people."
Ms Reeves pointed to "pensioners who are not turning the heating on when they need to because they're worried about the bills, mums who are skipping meals to ensure that their children get three proper meals a day".
The shadow chancellor criticised the Tories for rejecting Labour's plan for a windfall tax which would be used to cut consumers' gas and electricity bills, in a parliamentary vote on Tuesday.
However, Conservative former minister Robert Halfon and Mel Stride, Tory chairman of the Treasury select committee, had both indicated support for the policy.