Sinn Fein's MPs should take their seats in the House of Commons for debates on the future of Northern Ireland, a senior MP said today.
Conservative Laurence Robertson, chairman of the Commons Northern Ireland Select Committee, said it was a tragedy Sinn Fein's five MPs did not attend debates in the chamber on the future of Northern Ireland.
He said the party's policy meant they were not serving the people of Northern Ireland very well but admitted there had been steps forward with Sinn Fein MPs attending meetings elsewhere in the Palace of Westminster.
Mr Robertson said he had raised the issue with the party's leadership - Gerry Adams and Martin McGuinness.
Until now, the MPs - Pat Doherty (West Tyrone), Michelle Gildernew (Fermanagh and South Tyrone), Paul Maskey (Belfast West), Francie Molloy (Mid Ulster), and Conor Murphy (Newry and Armagh) - have not taken their seats in the Commons as it would mean swearing allegiance to the Queen.
Speaking during a Commons debate on the future of Northern Ireland, Mr Robertson said: "(Sinn Fein MPs) should be coming here to argue the case. They do travel to Westminster, they do have meetings here in this building.
"But they won't come here to this chamber to discuss the issues. I would suggest that is a tragedy. If I could suggest to them they are not serving the people of Northern Ireland very well in their abstentionist policy because almost a third of the province is not represented here in this chamber.
"That is a tragedy for the people of Northern Ireland, regardless of whether they were nationalists, republicans or unionists."
Conservative MP Oliver Colvile (Plymouth, Sutton and Devonport) said progress had been made.
In a question to Mr Robertson, the MP said: "Is it not also the case that we have begun to make some progress? We have been able to open a dialogue of some sort. We have much further to go."
Tory MP Brian Binley (Northampton South) said it was "one of the great sadnesses" that Sinn Fein MPs were not attending tonight's debate in the Commons.