The British government has dismissed as unacceptable any suggestion that Sinn Fein MPs could take seats in the House of Commons without swearing the Oath of Allegiance.
Former Tory minister Mr Alan Clark raised the issue when he said Mr Gerry Adams and Mr Martin McGuinness should not be excluded from Westminster for refusing to swear allegiance to Queen Elizabeth.
He said the House of Commons had no authority to exclude the MPs and he regarded their absence as a "political omission".
Dubbed a political "dinosaur" by the Conservative leader Mr William Hague, after he said the only way to deal with terrorists was to shoot them, Mr Clark was criticised by the Home Secretary, Mr Jack Straw, yesterday for failing to understand the oath's importance.
Mr Straw said: "My view is that it is unacceptable. It is very important - and happens in almost every parliament in the world - that if you are elected a Member of Parliament you have to acknowledge the obligations that go with that and the way we do that in this country is an oath of allegiance to the crown."
The Ulster Unionist Party's security spokesman, Mr Ken Maginnis, said Mr Clark's comments were "totally illogical nonsense".
"I think Alan Clark regretted what he calls the misinterpretation of his `kill 600 terrorists in the one night' previous contribution to the debate on Northern Ireland and set out with a degree of desperation to make amends," Mr Maginnis added.