Transport minister Ruth Kelly said the government has spent £6m of taxpayers’ money on car travel over the past year – a rise of 8% on the previous 12 months.
At the same time fleets are being urged to consider alternatives to the car in order to reduce carbon emissions.
Opposition parties accused the government of ignoring its own advice on climate change.
Liberal Democrat MP Susan Kramer, the shadow transport secretary, said: “It is time to bring these spiralling costs under control. The government must justify this massive increase in car use. Climate change is the biggest threat our planet faces.
“It is vital that everyone does as much as possible to cut down on carbon emissions, and that includes ministers.
“Transport currently accounts for over a quarter of the UK’s CO2, with traffic emissions continuing to rise. The government must start to lead by example.”
The biggest spenders were former prime minister Tony Blair and deputy prime minister John Prescott with more than half a million pounds spent on car travel.
The biggest increase in spending came from former foreign secretary Margaret Beckett and the Foreign Office, up by more than a third.
A spokeswoman for the Department for Transport defended the figures.
She said: “The Government Car and Despatch Agency (GCDA) has done a lot of work to reduce fleet emissions.
“The average fleet emissions have been reduced by 22% since last year, which is quite a big reduction. About 45% of cars are now hybrids which present savings from better fuel efficiency and congestion charge exemption totalling £1,800 per car per year.
“The overall cost of car use has gone up, but the GCDA offers a highly specialised service and those costs reflect the nature of the job.
“Keeping costs down is very important to the agency and each purchase of a car is rigorously assessed to keep the costs as low as possible.”
The spokeswoman said she couldn’t confirm that car use had increased, because a breakdown of the costs is not available for security reasons.
“The agency is not immune to rising product, fuel or labour costs and the charges made by the GCDA reflect that,” she added.