The Scottish parliament voted by three votes to go ahead with the Holyrood scheme.
The decision to withold this information was defended by civil servant Robert Gordon, the head of the executive secretariat at the time, when he answered questions on Tuesday. He denied that the then first minister Donald Dewar had misled MSPs.
Gordon said that the cost projections from DLE were estimates and that the final cost could be pared down. He said: "They were not costs that had to be met, but risks that had to be dealt with."
It was claimed two weeks ago that officials had broken the procurement rule governing the acceptance of the lowest bid, and last week it was alleged that that was not the only procurement rule to have been ignored.
Under the rules of the European Union, officials were obliged to explain why Sir Robert McAlpine's bid had been rejected. The inquiry was told that no explanation had been made.
Sir Robert McAlpine's director, David Boyle, wrote repeatedly to civil servants asking for a debriefing session but received no answer.
Boyle told the inquiry last week that the firm had been surprised that it had lost out to Bovis. He said: "It was a bit of a shock because we had understood that Bovis had been eliminated at an earlier stage."