Liz Truss has been accused of throwing Chancellor Kwasi Kwarteng “under a bus” by saying the decision to cut income tax for the richest was made by the Chancellor and not Cabinet.

Nadine Dorries, the former culture secretary who backed Ms Truss to be Prime Minister, criticised her remarks made on the first day of the Tory conference in Birmingham.

The plans to abolish the 45% tax rate on incomes above £150,000 a year has caused anger during the cost-of-living crisis, even among some Conservative MPs.

Ms Truss appeared to give Mr Kwarteng clear ownership of the move, saying they did not discuss the controversial plan with the wider Cabinet.

“No, no, we didn’t. It was a decision the Chancellor made,” she told the BBC’s Sunday With Laura Kuenssberg.

But allies of Mr Kwarteng insisted the decision was made “in lockstep” with Ms Truss herself.

Ms Dorries responded by tweeting that “one of” Boris Johnson’s “faults was that he could sometimes be too loyal”.

“However, there is a balance and throwing your Chancellor under a bus on the first day of conference really isn’t it,” she said.

Fingers crossed, she added, “things improve and settle down from now”.

The Chancellor’s allies sought to downplay suggestions of a rift.

A source close to Mr Kwarteng said: “While the Chancellor obviously makes all tax decisions, the Prime Minister and Kwasi are in lockstep on this.”

The row comes after Downing Street denied there had been a row between Ms Truss and Mr Kwarteng over how to deal with the pound as it plummeted in the wake of the announcement of plans to pay for £45 billion of tax cuts with borrowing.

The Prime Minister’s defence of Mr Kwarteng attending a private Champagne reception with hedge fund managers who stood to gain from a collapse in sterling following his mini-budget also appeared less than full-throated.

“I do not manage Kwasi Kwarteng’s diary, believe me,” Ms Truss told the BBC.