Previous chancellors have repeatedly frozen the levy in the past, but a 23 per cent increase in the duty is pencilled in for March.
Mr Sunak told MPs he would not comment on matters that are the responsibility of Chancellor Jeremy Hunt when asked to confirm that the rise will not go ahead.
“Having previously had his job, I always preferred it when the prime minister made absolutely no comments about future tax policy, so I will absolutely adhere to that,” he told the liaison committee.
Treasury select committee chairwoman Harriett Baldwin told Mr Sunak that the policy would mean extra taxes of “£6 billion ($7.3 billion) a year during a cost-of-living crisis”, and there was a need for a “better approach to fuel duty”.
UK's finance minister says he is focused on bringing down inflation as economy shrinks - video
“Tax decisions are those that are made by the Chancellor in fiscal statements and that’s the way it should be," Mr Sunak said.
At the time of Mr Hunt’s autumn statement in November, the Office for Budget Responsibility said a “planned 23 per cent increase” in fuel duty in March would add about 12p a litre to pump prices.
What is a recession? - video
The figure is based on a combination of the scheduled end of the 5p cut in duty, and the long-standing policy of duty rising in line with the RPI rate of inflation.
But no chancellor has increased fuel duty in cash terms for more than a decade and the Treasury insisted a final decision on the rate would not be made until the next budget, scheduled for March 15.