The Northern Secretary Paul Murphy said he was deeply disturbed by the arrest of a civil servant who worked for David Trimble and Mark Durkan suspected of spying for the IRA.
"I am very much aware of these arrests that have taken place. They are part of an ongoing police investigation," he said.
"These are very serious matters and what they do in an issue such as this is to undermine confidence and trust in the process, something myself and the British Prime Minister have been emphasising over the last few weeks."