One insider told Building that the Enric Miralles-designed project is over-budget as a result of excess tender offers and inflation. They said: "Tenders for the superstructure and cladding contract have come in above our cost requirements. Couple this with the effects of inflation and it will send the project past the £195m price cap."
The parliament's corporate body, the board legally responsible for the project, will now seek MSPs' approval for extra funds in addition to the £195m.
Scottish Conservative leader David McLetchie said any increase in the budget for the new parliament building was a "sick joke" at the taxpayers' expense.
He said: "I hope that the Scottish parliament will give short shrift to this third demand for yet more taxpayers' money to lavish on the new Scottish parliament building.
"It is absurd to suggest that a suitable building cannot be produced within a budget of £195m." The cost of the Holyrood building rose from an original quote of £40m to £230m before the new target of £195m was fixed last year.
Author David Black, who has spent three years researching the project, has estimated that the cost could eventually escalate to £300m. Black has also warned that MSPs might not be able to move into the building until after the 2003 elections.
A Scottish parliament spokesperson said Black's claims were "inaccurate".