MSPs are sticking to current designs

Presiding Officer Sir David Steel told MSPs that Mr Miralles was unwell and it was not certain when he would be back at his desk.

However, Sir David gave assurances that the plans remained in hand and co-partners - an Edinburgh-based firm - would see things through.

It emerged late on Wednesday that Mr Miralles had been on a lecture tour of the United States when he was taken ill.

Some reports said he was in need of brain surgery.

On the BBC's Newsnight Scotland programme, Sir David further reiterated that the project was safe.

'Immense effort'

He believed the most important stage of Mr Miralles' involvement, which was the initial vision for the new building, had now been completed

Sir David had earlier told MSPs: "Mr Miralles has put in an immense effort to finalise the design.

"It is not clear how soon he will be able to return to work, but I know that we would all wish him a speedy recovery."

Sir David Steel: Miralles disclosure

A spokeswoman for the Scottish Executive said that it has no detailed information about the condition of Mr Miralles, but stressed that work on the parliament building would press ahead.

Speculation about the architect's health followed the vote by MSPs to plough on with the current building work at a revised cost of �190m..

An amendment by Liberal Democrat Donald Gorrie, which would have seen the project halted and other options considered, was defeated by 67 votes to 58.

A further amendment by Labour's Gordon Jackson, which supported the present scheme but with additional guarantees over funding and completion dates, won through by 67 votes to 58.