Mr Miralles came up with the design

Mr Miralles was commissioned to design the Holyrood building which is behind schedualed and massively over budget.

The parliament confirmed on Friday evening that Mr Miralles was comfortable and that his family have requested that he be left to recuperate.

A spokesman said: "We know that his condition is comfortable but that his family wish to see their privacy respected."

He added: "As is clear from the advanced state of designs presented to MSPs earlier this week, relatively little work is required to finalise them.

Request for privacy

"Enric's present state of health does not impede progress and we fully accept the design team's assurances that the work required to finalise the project will be completed on schedule.

"In view of Enric's family's request for privacy we do not propose to make any further statements as to his health unless there is significant news to report.

Sir David Steel: Knows details of the illness

"We hope that the media will respect that request and allow him the time and space to recover so that he is able to return to the project at the earliest opportunity."

Details of Mr Miralles' illness are not being released, but it was confirmed that Presiding Officer Sir David Steel and parliamentary officials know what they are.

It is not being revealed when the Catalan took ill.

The spokesman acknowledged Mr Miralles' absence from the project was likely to be protracted.

Crunch debate

However, he insisted the Holyrood scheme was a joint effort between Mr Miralles and an Edinburgh firm and said it had now reached a stage where the architect's participation could be missed for a short time.

MSPs had only learned of Mr Miralles' illness at the crunch debate on the Holyrood project on Wednesday.

Sir David had told them he was "out of commission" and it was unclear when he would return to work.

Earlier this year the total estimated cost for the project was rumoured to be as high as �230m.

But a report into the matter by independent expert John Spencely put the figure at �195m.