The head of the UK Statistics Authority has rebuked the Home Office for being ''highly selective" in briefing drug seizure figures "in order, it seems, to show the UK Border Agency in a good light''.

Sir Michael Scholar has demanded the immigration minister, Damian Green, assure him that the advance briefing of partial class A drug seizures figures was not done to generate positive news coverage days ahead of the release of national statistics that showed an actual annual decline in the volume of drug seizures.

"Were it to be the case, the authority's view is that this would be highly corrosive and damaging public confidence in official statistics," Scholar warns Green.

The statistics authority statement says the latest Home Office statistics published on 10 November showed a fall in the volume of seizures of class A drugs in the most recent period.

"This contrasts with the 4 November press release, which highlights a large increase in seizures albeit for a different time period. The 4 November press release, which appears not to have been published on either the Home Office or the UK Border Agency websites, and seems to have been distributed only to a select group of journalists, makes no reference to the forthcoming bulletin," says Sir Michael's statement.

He says that the "good news" figures were produced without any involvement by, and without the knowledge of, the Home Office's statisticians.

"It is highly selective in its choice of statistics, in order, it seems to show the UK border agency in a good light."

It is understood that a Home Office briefing was held for members of the Crime Reporters' Association only and at least one journalist was told he was not welcome. The briefing generated headlines such as: "Class A drug seizures rise - UK Border Agency".

But when the national statistics were released later that week they showed that heroin seizures had almost fallen by almost half and cocaine seizures were down a quarter in 2010/11. The earlier figures only applied to UKBA seizures and to a different period from April to September.

The Statistics Authority says it considers the selective briefing of the drug figures in advance of the official statistics to have been irregular and inconsistent the ministerial code and the civil service code on official statistics.

A UKBA spokesperson said: "We regularly use management information to highlight our operational work, while continuing to take our responsibilities under the UK Statistics Authority's code of practice seriously. We will be replying in due course."

The Home Office said it may respond later on Tuesday to the Statistics Authority letter.