The move comes as it emerged that next week M&E union Amicus is to call for Hotchkiss, the ductwork contractor on the T5 project, to be removed over its failure to sign the pay and conditions deal for the site, known as the major projects agreement.
BAA and Laing O'Rourke decided to take Geofirma off its soil stabilisation services contract following a two-week investigation by BAA's internal auditors.
In a statement, BAA confirmed that contractor CA Blackwells has removed its supplier Geofirma from the T5 programme. It said: "As a result of concerns over accounting irregularities, McArdles has been appointed to provide soil stabilisation services with immediate effect."
The statement added that the removal of Geofirma would have no impact on the T5 programme, saying: "It would be premature to comment on details until investigations are complete, but BAA is extremely confident that it will not suffer any financial loss and will get full cost recovery through the supply chain."
A BAA spokesperson said that a financial investigation into the firm was continuing. He said: "We have not closed the book on this yet. [Our inquiries] will take weeks, rather than months." It is understood that BAA is looking at irregularities surrounding a seven-figure sum, and that no other contracts are under investigation.
Geofirma and CA Blackwells both refused to comment.
Ductwork contractor Hotchkiss is also facing scrutiny this week, as M&E union Amicus is concerned the firm has not signed up to the major projects agreement struck last year.
The union is to demand that Hotchkiss join the pay and conditions deal or be removed from the project at a joint industry council meeting next Wednesday.
Hotchkiss is either in or out, but either way things will come to a head
Frank Westerman, Amicus
Amicus regional organiser Frank Westerman said that he was "sick and tired" of the "prevarication" on the Hotchkiss issue.
He said: "They're either in or they're out, but either way things are going to come to a head."
An insider on the T5 joint industry council told Building that the union was concerned about the way Hotchkiss was dealing with negotiations. He added that the union had grave concerns about the way that Hotchkiss employed its workers.
A T5 spokesperson said: "We would like Hotchkiss to operate under the principles of the MPA at Terminal 5 and understand that discussions to this effect are progressing well. We look forward to a positive outcome for all concerned."
Hotchkiss refused to comment.
At a site meeting on Monday, a union representative called for the 30 workers, who represent about half those on site, to leave.