The top government statistician has said Tony Blair “clearly contravened” rules on the release of official data by talking about unemployment statistics before they were released.

A letter from Karen Dunnell, the national statistician, warned that the prime minister’s actions could undermine public trust in government figures. She told cabinet secretary Sir Gus O’Donnell that he should “bring this point to the attention of all at 10 Downing Street”. Earlier, Number 10 said the prime minister will “take into account” any concerns over his leaking of the latest unemployment data.

Speaking at the TUC conference earlier this month, the prime minister let slip that the latest joblessness data would show a decline in the number of people claiming Jobseeker’s Allowance. “Tomorrow we will see a fall in unemployment, which is very welcome indeed,” he told union members. Ministers see the data in advance of its publication but are not allowed to make it public until it is formally released by the Office for National Statistics.

Education secretary Alan Johnson has also been under fire for allegedly ‘burying’ bad news.  The Statistics Commission accused Johnson’s political advisers and “senior officials” at his department of interfering in the release date of this year’s Key Stage 2 and Key Stage 3 national test results. The DfES has insisted that the correct procedures were followed and that it had followed the rules governing the release of statistics.