Sir Keir Starmer’s Cabinet is united behind plans to dramatically scale back the winter fuel allowance, Downing Street has insisted amid mounting calls, including within Labour ranks, for the Government to soften the policy.

Ministers are “agreed” on the importance of “fixing the foundations of the economy” by taking tough and unpopular spending decisions, a Number 10 spokeswoman said of Monday’s meeting chaired by the Prime Minister.

Asked by reporters whether there had been any dissent over the planned cut, which will see all but the country’s poorest pensioners stripped of the winter fuel payment, she said there had been none.

“The Prime Minister opened Cabinet by stating the importance of fixing the foundations of our economy in order to carry out the Government’s mandate for change,” the spokeswoman said.

“He said that, given the scale of inheritance, this would be difficult and that tough decisions are unpopular decisions, but it is the tough decisions that will enable change for this country.”

Disavowing suggestions made by a Home Office minister on Monday’s broadcast round that the Treasury is looking at ways to mitigate the cut, No 10 said there had been no discussion of softening the impact of the policy.

Asked whether Dame Diana Johnson had been “freelancing” when she indicated the Government is considering doing more than encouraging further take-up of Pension Credit, Downing Street said the remarks had been “promptly corrected”.

It comes amid union unrest over the policy and ahead of a Commons vote on Tuesday, in which the Prime Minister is likely to suffer another backbench rebellion.

Some 17 Labour MPs have now signed a motion put forward by Neil Duncan-Jordan, one of the parliamentary party’s newly elected members, calling on the Government to delay implementing the cut.

The motion has also been backed by six of the seven MPs who lost the party whip in July after voting against the King’s Speech over the Government’s refusal to abolish the two-child benefit cap.

However, ministers continue to insist the cut is necessary to help fill a £22 billion “black hole” in this year’s budget left by their Conservative predecessors.

Unite union general secretary Sharon Graham accused Labour of deciding to “pick the pocket of pensioners” while leaving the richest “totally untouched” and urged Sir Keir to “do a U-turn” on means-testing the allowance.

She told BBC Radio 4’s Today programme: “We need to make sure that he is making the right choices and leadership is about choices. He needs to be big enough and brave enough to do a U-turn on this choice. It’s completely wrong.

“People do not understand how a Labour Government has decided to pick the pocket of pensioners and, at the same time, leave the richest in our society totally untouched. That is wrong and he needs to change course.”

Ms Graham called instead for a tax on the “1% wealthiest”, which she claimed would raise £25 billion rather than the £1.2 billion restricting winter fuel payments would save.

She said: “The wealthiest in the country have been at the front of the queue for 14 years. I want to see workers and communities now at the front of the queue and that is why we’re saying they must do a U-turn on this very, very, very cruel (policy).”

Meanwhile, Rail, Maritime and Transport (RMT) union general secretary Mick Lynch said the Government is making a “historic mistake”.

“They will have to do something about this historic mistake, otherwise we will start to see the consequences this winter,” he told a fringe meeting at the TUC Congress in Brighton.

Under the plans announced by Chancellor Rachel Reeves in July, winter fuel payments will be restricted to those receiving Pension Credit, meaning around 10 million pensioners will lose out this winter.

Ahead of the vote, Ms Reeves will speak at a meeting of the Parliamentary Labour Party on Monday in an effort to address backbench concerns.

Earlier on Monday, Home Office minister Dame Diana told the BBC the Government is working to ensure all pensioners who are entitled to Pension Credit claim the benefit, adding that she is “sure” other mitigations are being looked at by ministers.

However, Treasury sources said she “misspoke” in suggesting the Government is looking at doing more than encouraging further take-up of Pension Credit.