The Ulster Unionist MP Mr Jeffrey Donaldson is seeking an urgent meeting with the British Home Secretary, Mr Jack Straw, to discuss the alleged tapping of his telephones.
Mr Donaldson, a leading opponent of the Belfast Agreement, said RUC officers had informed him that the British government had ordered a special unit operating out of British army headquarters at Thiepval Barracks in Lisburn, Co Antrim, to tap his telephones.
He also accused the British government of authorising covert surveillance of other anti-agreement UUP members. He is demanding that Mr Straw show him records of authorisation permitting the tapping of his land and mobile telephones.
Mr Donaldson said he believed the surveillance began in 1999 but said he did not become aware of it until last year. He also believed that listening devices had been used to monitor UUP meetings.
Mr Donaldson said: "This is a very worrying development and a cause of concern for everyone. Any improper use of government powers has to be investigated. An MP has the right to go about their parliamentary duties without this kind of intrusion. The government has a duty to explain itself." The government was misusing the security services, he said. "These sort of powers should only be used if a security threat is posed by an individual.
"We are elected representatives wholly committed to democracy. The government is misusing the security apparatus for purely party political purposes. They are engaging in a breach of our civil liberties." An RUC spokesman yesterday said the force did not investigate any individual case unless it received a complaint.