The man alleged to be Britain's top spy inside the IRA is said to be under military protection at a former US airbase in the home counties.

Although Sinn Fein said he may still be in Belfast, Alfredo "Freddie" Scappaticci, named by newspapers as agent "stakeknife", is claimed to be being debriefed at the former base at Chicksands in Bedfordshire.

The base, home to Britain's Defence Intelligence and Security Centre, is one of the most secure military installations in the country.

The Guardian claims defence secretary Geoff Hoon personally gave authority to a series of gagging orders preventing the agent from being named.

Meanwhile, Irish premier Bertie Ahern has confirmed that he will raise the matter when he meets Tony Blair next week.