Transport secretary Geoff Hoon has attacked the Conservatives for wanting to increase the cost of motoring just as the global downturn begins to bite.
"A promise on fuel tax which David Cameron made to win headlines in July would now add millions of pounds to British families' tax bills," said Hoon.
"For all his smooth patter, the truth is Mondeo drivers would now be paying £2.10 a tank more."
In July of this year George Osborne launched the opposition's Fair Fuel Stabiliser, which reduced fuel duty as the price of oil rose, and increased duty when the price of oil fell beneath the Treasury forecast of $84 a barrel.
Brent Crude, the benchmark grade of crude oil, has now dropped to less than $65 a barrel.
The Conservatives weren't the only ones who failed to predict a drop in oil prices.
When the policy was launched Kitty Ussher, then Economic Secretary to the Treasury, said that the proposal "would mean a massive hole in the public finances".