Almost unnoticed, the Conservatives have made an historic shift in policy. They have ended the bi-partisan approach to Northern Ireland in general and the peace process in particular. The party's leading figures do not quite put it like that themselves. Iain Duncan Smith and his colleagues proclaim broad support for the process, while retaining the right to make criticisms. But these criticisms have become so regular and so intense that they amount to opposition to the Government's entire approach to Northern Ireland.

This opposition reached a new level of ferocity at the end of last week. The Conservatives' Northern Ireland spokesman, Quentin Davies, appeared on BBC Radio 4's Today programme to protest about the Government's plans to allow Sinn Fein some office space at Westminster. Mr Davies has always looked as if he is on the verge of exploding. Quite often in the past his own party has been the cause of his suppressed fury. Mr Davies is a strong supporter of the euro, a conviction that sorely tests any leading Conservative. Still, Mr Davies has managed to stay more or less calm on the surface. Last week he exploded. The prospect of Sinn Fein MPs sharing an office or two at Westminster was too much for him. The decision was "outrageous ... an insult to Parliament ... caving into Sinn Fein/IRA".

The Conservatives' unflinching line is significant for two reasons. In most policy areas the party does not have a policy. This is entirely sensible for a party that has suffered two landslide defeats. Even on the euro, where it has a policy, it has lost the confidence to speak out. Mr Duncan Smith, who passionately opposes the euro, prefers to keep his passion to himself. On a whole range of other issues the party is reviewing policies. Only on Northern Ireland has it taken a measurably clear stance since the general election.

The lead has come from Mr Duncan Smith, the other significant factor. In his first set-piece speech after becoming party leader last September he took Northern Ireland as his main theme. Having declared that he stood "shoulder to shoulder" with Mr Blair on the international crisis, which was then at its height, Mr Duncan Smith proceeded to move his shoulder away. Comparing the Government's latest manoeuvrings in Northern Ireland with its unflinching stand in the "war against terrorism", he declared that "We cannot allow the rule of law to be set aside in our own country at the same time as insisting the rule of law is upheld in other countries".

This provocative and mischievous intervention was ill-judged on several counts. In the international crisis the "rule of law" was being applied with a similar pragmatism to its application in Northern Ireland. The US and Britain were wooing several countries that harboured terrorists as Mr Duncan Smith uttered his defiant words. His intervention revealed a wilful mistrust of the peace process in Northern Ireland, a process that demands almost inhuman levels of pragmatic patience.

The Conservatives' current position is the climax of a long narrative that began heroically enough with John Major rising to the change of political mood that opened up in Belfast in the early 1990s. But by 1997 Mr Major had become a prisoner of his own party. Right-wing Conservatives were as sceptical over Northern Ireland as they were about Europe, making him virtually powerless in his dealings with the parties in Northern Ireland. In the last Parliament William Hague used to play the game of supporting the peace process and opposing policies aimed at sustaining it. The difference now is that the balance between opposition and support has swayed further to opposition and at a time when the Conservatives are in an introspective mood in all other policy areas.

The Conservative position jars more because of the current state of the peace process itself. As ever, it is in an almost terminal position. David Trimble leads a divided party. He fumes at the latest concessions to Sinn Fein. From the Sinn Fein perspective the concession over office space is nowhere near enough. On other fronts it protests that the British Army presence in Belfast is currently more visible than in recent years. Its leadership still has doubts about the status of the reformed police force, seeking greater accountability and transparency. On the other side, the Unionists believe they have conceded more than enough as far as reforms to the RUC are concerned.

More widely, the Sinn Fein leadership is impatient. It seeks a debate in the New Year about constitutional changes leading to a united Ireland. Some leading Unionists fear that is precisely where the whole damned show is moving.

Yet this latest whirl of conflicting, irreconcilable positions is a more rosy near-terminal position than the other recent near-terminal positions. The Sinn Fein leadership understands privately that the British Army presence will not greatly be reduced yet. It dares to point out to its dissidents that it is the continued activities of the Real IRA – as well as the Protestant terrorist groups – that make it impossible for the British Army to withdraw. Mr Trimble recognised that the IRA's decommissioning gesture was an important moment and one he seized to regain some political momentum. On the whole the Northern Ireland Secretary, John Reid, is respected by the different parties, although they have all got into the habit of wanting to deal with Tony Blair and Jonathan Powell in Downing Street.

But the main reason for the slight cause for optimism is the relative success of the Northern Ireland Assembly when it has met. These local politicians have spent much of their recent lives hobnobbing with presidents and prime ministers. For all their posturing on the international stage they have had little direct power over what happened to their constituents. In the context of a devolved Britain they have got some real power now. Most of them seem fairly keen to exercise it. Some are even daring to predict that when the Assembly meets in the New Year it might actually meet for more than a few months before having to be "parked" or suspended again in another crisis.

This is only possible because of the extreme pragmatism of the Government, bending words and commitments to their limits, making concessions to one side and then the other. As a result a political settlement of sorts is still in place.

There is an alternative to a political settlement. It is no political settlement and the collapse of the peace process. To find out what happens in those circumstances take a look at the Middle East this weekend.