Sinn Fein has denied any involvement in alleged republican intelligence gathering at Stormont and said it did not benefit from any information leaked from the offices of its political opponents.
The denial follows the arrest of a civil servant yesterday evening in connection with alleged IRA infiltration of the offices of the First and Deputy First Ministers.
Sinn Fein spokesman Conor Murphy said the arrest was part of a security force agenda to undermine the peace process.
"Many people are also wondering is there a McCarthy-like type of witch-hunt going on against Catholic civil servants who happen to live in nationalist areas," he added.
The man arrested this morning was Gerard Willis, from Andersonstown in west Belfast, who had worked in the offices of both the First and Deputy First Ministers. His arrest was part of an ongoing investigation into sensitive documents found during a series of raids in nationalist areas of Belfast several weeks ago.
Four men, including two with links to Sinn Fein, have already been charged with possessing information which could be of use to terrorists in connection with these documents, some of which are believed to have originated in the British Government's offices in Stormont.