Liz Truss has been accused of throwing 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 Truss to be Prime Minister, criticised her remarks made on the first day of the Conservative Party conference in Birmingham.
The plans to abolish the 45 per cent tax rate on incomes above £150,000 a year in England, Wales and Northern Ireland has caused anger during the cost-of-living crisis, even among some Conservative MPs.
Truss appeared to give 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.
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 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 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," Truss told the BBC.
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