Veteran left-wing politician Tony Benn has suggested Sinn Fein should have a rethink about taking its seats at Westminster.
Labour left-winger Tony Benn
Sinn Fein won five seats in the general election but has a policy of abstentionism.
This means its MPs refuse to swear the oath of allegiance to the Queen and so cannot enter the commons chamber.
Mr Benn, who retired as an MP in 2001, says now might be a good time to change its policy on how it regards the oath.
Mr Benn said he personally objected to the oath but was prepared to take it under protest to get into the commons.
"The thing about it that's offensive is that it requires MPs to swear allegiance to the Queen.
"If you're an MP your allegiance is to your constituents, to your party to your conscience so really MPs have to lie in order to sit in Parliament. I had to tell 17 lies."
Mr Benn said he understood Sinn Fein's position on British sovereignty but still thought it made good political sense for them to put their point of view across in the Westminister chamber.
"It's entirely for Sinn Fein to decide, but I wondered whether this wouldn't be a time to rethink the position, he told BBC Radio Ulster's Talkback programme.
"You know Gerry Adams appealed to the IRA to engage in the political process and one way of restarting the dialogue would be for Sinn Fein to come to the House of Commons.
"So many people in Britain still think of the situation in Northern Ireland as a foreign situation whereas really it's the biggest domestic issue in British politics and has got to be resolved by dialogue.
Meanwhile Sinn Fein MP Michelle Gildernew has called on the government to lift financial sanctions imposed on her party.
The sanctions were imposed on republicans after suspected IRA involvement in the Northern Bank robbery in December 2004.
But Ms Gildernew claimed they should be removed following Sinn Fein's recent successes in the Westminster and local government elections.
"The British government does not have one vote in Ireland," she said.
"The new British Secretary of State, Peter Hain, must now end the sanctions programme against our electorate and get back to the job of making politics work."
Meanwhile the Irish justice minster, Michael McDowell, has angered Sinn Fein by again ruling out speaking rights for Northern Ireland's MPs in the Irish parliament, the Dail.