It is not the first time the government has come forward with some extra measures which aren't in the agreement

David Trimble

After an emotionally-charged Commons debate, MPs backed the government plans for the controversial move by a margin of 322 votes to 189.

The rule change was vehemently opposed by the Tories who ended cross-party support for government Northern Ireland policy in protest.

A handful of Labour MPs as well as Ulster Unionists and Democratic Unionists were also among the opponents, some of whom argued the rules were being bent for people with "blood on their hands".

Speaking on BBC Radio 4's Today programme Mr Duncan Smith said: "We have now two classes of MPs: one that comes in to take the money and has no responsibility to this country and the monarch, and others who have those responsibilities and must make a full declaration and have responsibilities to our constituents.

"I think that is not fair. This concession was given them without anything in return - that is what angers us."

Ulster Unionist leader and Northern Ireland First Minister David Trimble told the same programme that the decision to allow Sinn Fein access to facilities was not part of the Belfast agreement.

"It is not the first time the government has come forward with some extra measures which aren't in the agreement.

Davies accuses Sinn Fein of having MPs' blood on their hands

"We had a negotiation, came to an agreement, which involved quite significant compromises from various sides and then we find subsequently that one party is treated by government in a rather favoured way, in that further measures are made."

But Sinn Fein President Gerry Adams, speaking during a visit to Cuba, welcomed the vote.

He said his party intended to make full use of the facilities "not just to represent our constituents but also to build in England support for an end to the union".

Sinn Fein's MPs have consistently refused to swear the oath of allegiance to the Queen, which has left them barred from the parliamentary privileges afforded to other MPs.

The change means the four Sinn Fein MPs - Gerry Adams, Martin McGuinness, Pat Doherty and Michelle Gildernew - can enter the Commons precincts when Parliament returns in the New Year.

As well as using support services, the MPs can each claim �107,000 a year in allowances to cover staff salaries and expenses.

Maintaining momentum

Opening Tuesday's debate, Commons leader Robin Cook said the move was a "limited step".

"We are more likely to secure further decommissioning if we demonstrate that we are willing to maintain the momentum on our side," he continued.

Mr Cook said the Tories were ending bipartisanship on a move that would only restore the position to that in place under the last Conservative government.

Sinn Fein MPs had rights to Commons services until 1997, when then Speaker Betty Boothroyd barred access for the first time to those not taking the oath - a decision endorsed by her successor.

Since then, there had been historic developments in the Northern Ireland peace process, argued Mr Cook.

Shadow Northern Ireland secretary Quentin Davies said his party opposed the move in principle, saying MPs refusing to take their seats had never been allowed Commons allowances.

Preventing violence?

Mr Davies accused ministers of giving away "endless concessions" and getting nothing in return instead of keeping up the pressure on Sinn Fein.

Eastbourne MP Nigel Waterson asked how he could explain to his constituents that new benefits were being given to some of the people responsible for the murder of their previous MP, Ian Gow.

Mr Gow, as well as fellow Tory MPs Airey Neave and Sir Anthony Berry, were murdered by the IRA before its declaration of a ceasefire.

Mr Cook argued the whole point of the peace process was to prevent such violence in the future.