Former MI5 agent David Shayler, from Middlesbrough, will be robbed of his right to a fair trial on secrets charges if he is barred from arguing that what he did was in the public interest, his defence QC said yesterday.

At a pre-trial hearing held at the High Court, in London, Edward Fitzgerald QC was challenging prosecution argument that the alleged crimes were "absolute offences" and that issues such as disclosure in the public interest were irrelevant.

The 35-year-old former spy faces trial at the Old Bailey on three charges relating to an article in the Mail on Sunday in 1997 claiming that agents in the 1970s tapped the telephone of former Northern Ireland Secretary Peter Mandelson and kept a file on Jack Straw.