The Labour boss acknowledged soaring fuel prices clobber businesses and “hit family finances hard”.
And he told The Sun “nothing” in their current plans requires to raise “additional money” beyond the measures already announced.
But Sir Keir failed to categorically state fuel duty would not increase under a Labour government.
It comes as the party has given a cast-iron “triple-lock” commitment it won’t increase national insurance, income tax or VAT.
But the move has sparked fears Labour might be planning to raise revenues in other ways.
The Sun has backed drivers as part of the Keep It Down campaign with rates of fuel duty not rising since the start of 2011.
On whether Labour would retain the freeze, which stops prices rising with inflation, Sir Keir said: “Soaring fuel prices hammer businesses and hit family finances hard.
“Like Sun readers we want lower taxes on working people which is why we’ve also campaigned against fuel duty rises this Parliament.
“Nothing in our plans requires us to raise any additional money beyond measures already announced.
“Labour will grow the economy so we can get money back into the pockets of hard working Brits.”
