Northern Ireland's First Minister, Mr David Trimble, called on the Northern Ireland Secretary to take action against Sinn Féin in the wake of "the dramatic events which unfolded today".
He told reporters: "What we suspect is that there has been an IRA intelligence operation directed at the upper echelons of Northern Ireland's government for some time".
He said the "challenge now is for John Reid to take an appropriate response".
Mr Trimble said he was going to see the British prime minister early next week to discus this week's developments which he described as "a vindication for me and my colleagues".
Two weeks ago UUP members announced their intention to resign from the executive in the New Year unless action was taken against republicans who, the UUP said, were consistently breaching their ceasefire.
The police raid on the Sinn Féin offices has been denounced by the party, who described it as "highly political" and aimed at smearing the party.
