There have been problems with windows on the building

George Reid had summoned them to a meeting in Edinburgh on Tuesday to explain the latest �37m increase in the cost of the building.

He has obliged the consultants to cap their fees for the remainder of the contract period.

The most recent budget increase, taking the price to �375m, angered MSPs across the political divide.

Mr Reid said on Tuesday that the reasons for the rise included work on windows which were not fitting perfectly and had to be made wind and watertight.

In all, �18.75m was due to delays and further problems encountered on site.

I put to all the participants that they should consider in the public interest... a reduction in the money they receive George Reid Presiding Officer

Delays in completing the MSPs' block added �1m to the cost and �5m has been set aside to cover future unforeseen problems.

A further �8.25m was set aside for project construction manager Bovis Lend Lease, while VAT accounted for �4.6m.

And �6.1m of the increase was taken up by fees for consultancy firm Davis Langdon Everest, architects EMBT and Bovis Lend Lease.

MSPs on the parliament's corporate body met officials from the three companies on Tuesday.

Mr Reid described the talks as "extremely robust".

He said these latest fees, as well as those already due to the firms, would be capped.

Talks will now be held with the companies to set the level of the cap.

Projected increase

Mr Reid said: "I put to all the participants that they should consider in the public interest, because it is a matter for the public purse, a reduction in the money they receive.

"I'm happy to say we have today secured the agreement of all the consultants to cap their fees to the end of the project.

"In the public interest that cap will include a reduction in fees in respect of the latest projected increase in costs."

The price of the building is now estimated at �375m

Scottish National Party leader John Swinney said the project contractors should also be made to have their fees capped.

"It's time to tell them enough is enough. We have to call a halt to the Holyrood gravy train," he said.

Tory leader David McLetchie said Mr Reid's statement was "far too little too late".

But First Minister Jack McConnell said capping the consultancy fees "sent the right signal".

"This is exactly the right decision and the decision the public expected," he said.

"It is the correct action to be taken to protect the taxpayers' money."

Work completed

Mr McConnell is considering whether his promised investigation into the Holyrood project should take the form of a parliamentary inquiry.

Mr Reid has "warmly endorsed" Mr McConnell's promise of an inquiry.

He said parliament and construction staff involved in the project should not be asked to give evidence until their work is completed.

However, Mr McLetchie said that a parliamentary inquiry was "not good enough".

"There will be grave public suspicion that this is being swept under the carpet," he said.