MI5 tactics under question

A former Special Branch officer has confessed that he lied to Carol Thatcher's primary school teacher as part of an MI5 investigation into the teacher's alleged Communist sympathies.

The detective has admitted that he and a colleague posed as ordinary policemen investigating an alleged mail order fraud in an attempt to interview Madeline Haigh, a peace activist in the West Midlands.

Mrs Haigh, who taught the former Prime Minister's daughter at a boarding school in Hertfordshire in the late 1960s, was targeted after an MI5 informer in her Quaker peace group had claimed she had shown interest in the Communist Party.

The detective has also conceded that Special Branch officers routinely lied or invented cover stories to investigate suspects such as Mrs Haigh. His admissions have raised fresh questions about the tactics used by MI5 and the Special Branch to investigate alleged subversion by British citizens, ranging from animal rights activists to peace campaigners.

Mrs Haigh, then a housewife in Sutton Coldfield, was among thousands of peace activists whose life and activities were investigated by MI5 at the height of the campaign against cruise missiles in the 1980s.

The detective, known only as Keith, claims in a BBC2 documentary being broadcast tonight, True Spies, that Mrs Haigh's involvement in a local peace group in 1981 made her a legitimate target for MI5 and the Special Branch.