A senior Ministry of Defence official responsible for preventing the disclosure of military secrets has been arrested under the Official Secrets Act over the leaking of the memoirs of Dame Stella Rimington, the former head of MI5.

In a move which has shocked Whitehall, Colin Davenport, 58, was interviewed by special branch officers and bailed to appear at a central London police station next month.

Mr Davenport, who is a member of a secretive MoD secretariat responsible for highly sensitive security matters, was a member of a small Cabinet Office committee who vetted Dame Stella's manuscript.

Officials in the MoD were furious that she decided to go into print, saying that it would undermine their attempt to prevent former SAS soldiers from publishing their memoirs.

They helped to mount a vicious media campaign against the former MI5 chief and succeeded in preventing her from mentioning the SAS in her book even when she referred to events in which the role of the special forces had been publicly admitted.

A manuscript of her memoirs, Open Secret, was leaked to the Sun in September 2000 under the headline, "MI5 chief in book sensation". In her memoirs, published last September, she described the leaking as a "rather laddish covert operation".

She wrote: "Selective briefings were given... The story was kept going when the Sun kindly returned the manuscript with much fandango to No 10 Downing Street."

MoD officials said yesterday that Mr Davenport was still working at the ministry. He gave evidence last week to the Commons defence committee which is conducting an inquiry into implications for Britain's security of the September 11 attacks on the US.