Either way, ministers and officials in the Department for Education and Skills have cut spending on mobile phone calls to just over pound;250,000 a year.

The department’s annual bill more than doubled between 1997 and 2002, when it reached nearly pound;380,000. But figures released by the Government show that spending on its 1,120 mobiles fell last year to pound;270,000.

That works out at an average monthly phone bill per civil servant of pound;20, less than half the amount spent by staff in the Department for Culture, Media and Sport and the Department for Trade and Industry and a third less than those in the Office of the Deputy Prime Minister.

So, how did the DfES make the the savings? Is it because it spends more time in schools, where mobiles are usually banned? Or has it switched to a cheaper network?

The department would only say that the reduction was due to better negotiated rates.

The lower bill is a promising sign for the department, which is trying to prove to the Treasury that it can be more efficient.

But Mark Prisk, Conservative MP for Hertford and Stortford and shadow paymaster general, was not impressed.

“Labour clearly believes it’s good to talk,” he said. “I think most teachers would be shocked by the amount the DfES is spending on mobile phones when it could be putting more staff in schools.”

But not all ministers and department staff have been having a happy time with their mobile phones. Up until 2000, only around one member of staff per year reported a lost or stolen mobile phone. Nine had similar problems last year, and this year seven staff have needed replacements so far.

The total figures are higher than those for any other government department.