The move followed the discovery of Andrew Hull, a research assistant to David Atkinson, Tory MP for Bournemouth, with another unnamed researcher and a guest in Tony Blair's office about 7.30pm.
Labour MPs said yesterday that they feared the three may have been there seeking confidential information, but Miss Boothroyd told the Commons in a statement that there had been "no malice involved" and she blamed the incident on an "excess of seasonal spirit and a mischievous walk-about".
In a Commons statement, Miss Boothroyd said that the police had investigated the matter and were satisfied that nothing had been taken or disturbed. "Nevertheless, it must be understood that it is a privilege to work in and to have access to the Palace of Westminster. I do not expect that privilege to be abused. I have therefore given instructions that the researchers concerned should have their passes withdrawn with immediate effects and until 1 February."
Mr Atkinson said that "in the light of the circumstances" the Speaker's action was "inevitable". Whether Mr Hull would continue in his employ was "a matter I have to consider", although he added: "if the Speaker regards it as sufficient punishment, I wi l l probably follow the Speaker's lead ..."
Some Labour MPs remain suspicious about the incident, not least because of the explantion Mr Hull has offered. After drinking in the sports and social club bar, Mr Hull has said that he and his companions got lost and "ended up wandering into [Mr Blair's] office".
Dale Campbell-Savours, MP for Workington, said many of his colleagues did not find it credible that three people "should walk the length of the Palace of Westminster and just happen to enter into Mr Blair's office".
He went on:"We believe that their motive was deliberate: that was, to enter, knowing they had no right to enter that office, and to do whatever they set out to do". He asked the Speaker to name Mr Hull's companions.
Max Madden, MP for Bradford West, protested that "virtually any Tom, Dick, or Harry can be issued with a pass to this place", while David Winnick, MP for Walsall North, said there was a feeling on the Labour benches that this was "a sort of minor `Westminstergate' - a deliberate attempt to find out information".
Miss Boothroyd insisted that she had made extensive inquiries. "I am totally satisfied no malice was intended."
In the wake of the incident, police have suggested changes to the security arrangements at the Opposition leader's office, while, earlier yesterday, Mr Blair himself said that it was unclear whether the incident had any significance.