Suella Braverman, the home secretary, has accused fellow Tory MPs of staging a “coup” by forcing the UK government to abandon plans to axe the 45p top rate of income tax, as a new rebellion on benefit cuts erupted.

In a sign of the acrimony engulfing Prime Minister Liz Truss’s Conservative party, Braverman said she was disappointed that former cabinet minister Michael Gove and other MPs had forced a U-turn on the tax plan.

“I am disappointed that members of our party staged a coup, effectively, and undermined the authority of the prime minister in an unprofessional way,” she told a Telegraph fringe meeting at the Tory party conference in Birmingham.

Meanwhile, Truss is braced for a fresh rebellion over her economic plans, with senior Conservative MPs threatening to vote against her if she decides to cut welfare benefits in real terms next spring.

There was also confusion over the timing of the publication of the government’s debt-cutting plan — which will be set out alongside official forecasts — with chancellor Kwasi Kwarteng saying November 23 remained the planned date.

But his allies confirmed a report in the Financial Times that he was looking to bring it forward. “It will be done by November 23,” said one. “If we can bring it forward, we will try to do that.”

Treasury insiders said a change in date would first have to be notified to parliament, which does not return until October 11. Government officials said on Monday that Kwarteng hoped to announce his debt-cutting plan later this month.

The £45bn of unfunded tax cuts announced by Kwarteng in his “mini” Budget on September 23 has left the government looking for public spending cuts, including a possible squeeze on benefits.

Truss is looking at raising benefits in line with average earnings growth rather than inflation, a controversial move that has raised concerns among Tory MPs given the cost of living crisis.

Average earnings growth including bonuses was 5.5 per cent between May and July, according to the latest official figures, while inflation is almost twice as high, at about 10 per cent.

But Truss, who has already been forced into one U-turn this week over her proposal to axe the 45p top rate of income tax, is now under pressure from some Conservative MPs to change course on her benefits plan.

Penny Mordaunt, leader of the House of Commons, became the first cabinet minister to speak out against the policy on Tuesday.

Mordaunt, in a clear breach of cabinet collective responsibility, said it “makes sense” to increase benefits in line with inflation.

“I’ve always supported — whether it’s pensions, whether it’s our welfare system — keeping pace with inflation. It makes sense to do so,” Mordaunt told Times Radio.

“We want to make sure that people are looked after and that people can pay their bills. We are not about trying to help people with one hand and take away with another.”

Downing Street believes it would not be fair to give people on benefits increases of 10 per cent when wages in the public and private sectors are rising much more slowly.

However, Truss has committed to keeping the pension “triple lock” under which pensioners will see their payments rise by whichever is highest out of inflation, average earnings growth or 2.5 per cent.

Damian Green, former deputy prime minister, said that he and other MPs would not vote for the benefits policy in the House of Commons. “No, I wouldn’t approve of it. And no, I don’t think it would get through parliament,” he told LBC.

Mel Stride, Conservative chair of the Commons Treasury select committee, told the BBC he did not know if he could vote for real-term benefits cuts. “I’d have to think long and hard about that,” he said.

UK markets have steadied following the government’s U-turn on scrapping the 45p top rate of income tax on Monday.

The pound rose 0.6 per cent on Tuesday to its highest point in a fortnight against the dollar, touching $1.14. The yield on 10-year government debt, which rises when prices fall, dropped 0.09 percentage points to 3.86 per cent, as traders wait for more details about how the government will fund its fiscal plans.

Additional reporting by Delphine Strauss and Ian Johnston