The Planning Tribunal has rejected an application by builders Joe McGowan and Tom Brennan to have their legal costs paid by the State.
The pair are believed to have run up a bill of around €2.6m due to their dealings with the inquiry.
In his ruling on their costs application, tribunal chairman Judge Alan Mahon said Mr Brennan and Mr McGowan had colluded to mislead the tribunal and he described their lack of co-operation as extensive and unrelenting.
He said they had also conspired to conceal the true nature of their relationship with former minister Ray Burke, to whom they were found to have made corrupt payments.
For these reasons, Judge Mahon said, it was fair and reasonable to withhold costs from the builders.