The decision to build a new base for MI5 in NI has been criticised by a member of the Policing Board.
MI5 officers were based at Stormont Castle during the Troubles
Brendan Duddy, who for years acted as a secret link between republicans and the British government, said there was no longer any need for the agency.
He said constructing the complex was akin to an "air raid shelter being built after the war was over".
The security services will assume responsibility for national security matters in the province next year.
"People who don't know how security services work - like MI5, MI6 and the various other ones throughout the world - have all sorts of fantasies and notions," he said.
"What I am saying to MI5 is tell us what you are doing here.
"From a republican point of view, people feel simply that they are here to watch the IRA.
"I am saying that the IRA has stood down. The arms have been decommissioned and we don't need this type of rumour."
The M15 complex is being built at Palace Barracks in Holywood, County Down.
The organisation is due to take over the lead role in intelligence involving national security in Northern Ireland by the end of 2007.
Until now, the PSNI Special Branch has had overall responsibility.
In future, while police handlers will continue to work with individual agents they will, in some cases, report back to MI5.
During the Troubles, MI5 officers were based at Stormont Castle - their shift of premises coincides with a shift of role.
MI5 works from its headquarters at Thames House in London.
Its current chief, Dame Eliza Manningham Buller, is a former head of the service's Irish counter-terrorism desk.