Rishi Sunak left the door open to a 12p fuel duty rise in the Spring Budget as he was grilled by MPs on Tuesday afternoon.
Appearing before the liaison committee of senior Commons chairmen, Mr Sunak was asked at the liaison committee if he would stop Jeremy Hunt, his Chancellor, introducing a proposed increase of 23 per cent that was pencilled into Government forecasts last month.
He replied: "Having previously had his job, I always preferred it when the Prime Minister made absolutely no comment about future tax policy, and so I will very much adhere to that."
Harriett Baldwin, the chairman of the Treasury committee, noted this would amount to £6 billion a year during a cost-of-living crisis, telling him: "Surely you're not going to let the Chancellor get away with 12 pence a litre more on fuel."
But Mr Sunak said he would let Mr Hunt make the decisions and "announce them in the normal way", adding: "Whether I was chancellor or as Prime Minister, I would say exactly the same thing - tax decisions are those made by the chancellor in fiscal events."
Tuesday's session marked one of the first major scrutiny tests for Mr Sunak, who has yet to give a press conference since unexpectedly becoming Prime Minister eight weeks ago.
