Northern Ireland prosecutors say a British Army spy who worked inside the Irish Republican Army will be investigated for his alleged role in at least two dozen killings.

The director of public prosecutions, Barra McGrory, made the announcement Wednesday citing evidence compiled by Northern Ireland's police complaints watchdog into the shadowy activities of the agent codenamed Stakeknife.

Stakeknife allegedly ran the IRA's internal affairs unit responsible for identifying, interrogating and killing spies and informers. McGrory said he expected Northern Ireland's police to appoint an independent investigator to look into Stakeknife's involvement in such IRA killings and the role played by his military overseers.

In 2003 Stakeknife was publicly identified as IRA veteran Fred Scappaticci, a Catholic west Belfast native of Sicilian background. Scappaticci denied the allegations and disappeared from Belfast.