THE architect designing the Holyrood Parliament is on a collision course with some MSPs over the shape of the debating chamber, after a day of presentations by Mr Enric Miralles that left the issue unresolved.

Some MSPs left their meetings with the Catalan architect saying they could not bring themselves to vote for his plans if the seating configuration was left unresolved, while Mr Miralles, having evolved the proposed horseshoe-shaped chamber into what was variously described as a banana or boomerang shape, said he would find it extremely difficult to change it at this stage.

The strong likelihood remains that when the issue is debated tomorrow on the Mound his plans, which have the backing of First Minister Donald Dewar, will gain a majority. But the SNP's Margo MacDonald and Mr Donald Gorrie of the Liberal Democrats have now tabled an amendment to put the project on hold to give MSPs a chance to re-evaluate the issues.

Mr Dewar's motion tomorrow endorses the choice of Holyrood as the site and authorises the corporate body of the Parliament to proceed with existing plans, timescales, and costings.

The amendment calls for the creation of a special committee to work on the matter during the summer recess; to reconsider the merits of Holyrood versus Calton Hill and the temporary home on the Mound; to empower that committee to advance the Holyrood scheme if it is the best option ''at high quality and increased costs''; to limit site work to preparation in the meantime; and to negotiate a revised timetable in that event.

Mr Gorrie said a swift evaluation of the site options could be done, but if Holyrood were to proceed it had to be done properly and in line with the wishes of MSPs. He said he had made clear to Mr Miralles that his personal dispute was not with him but with the original choice of site.

The architect held a series of question-and-answer sessions with MSPs yesterday but only around a quarter of members took advantage of the offer. Many left saying they were still unhappy about the flattened seating configuration, but Mr Miralles said of the prospect of changing it: ''A radical change would be very difficult. That would produce strong complications.''

That put him on a collision course with some members, such as Highlands and Islands MSP Mary Scanlon, who said the proposed chamber was reminiscent of a Stalinist chamber, with members facing front.

SNP business manager Michael Russell said: ''My concerns have not been diminished by the presentation I've seen and I will certainly be thinking very carefully about the position I take on Thursday.

''I have worries such as the design of the debating chamber, which has changed out of all recognition in relation to what the Parliament expected, and I certainly haven't heard in there the answers I would have liked.''

He said of the seating plan: ''The word I heard in there was a banana. I think it is likely to be a banana skin for Mr Miralles and his design team. The debating chamber is not likely to produce any debates. Staying on the Mound is an attractive proposition for me at the moment. Another is pausing on the whole thing and looking at all the options again.''

Green MSP Robin Harper said: ''What worries me most is that he seems to be very reluctant to change the design of the chamber.''

But Ms Karen Whitefield was one of several Labour MSPs who emerged to defend the design. ''I think it is very exciting and innovative, a new Parliament for a new century which can make Scotland an example for the rest of the world to follow,'' she said and colleagues spoke of a chamber that would promote consensus.

Meanwhile, Edinburgh planning convener Bob Cairns described the present Assembly Hall chamber as a ''clapped out church hall'' at a meeting of the city council policy and resources committee.

The Conservative group had called on the committee to support the cross-party moves in the Parliament for a review of the proposed move to Holyrood, claiming the site had been chosen by Donald Dewar without consultation.

Labour administration leader Donald Anderson pointed out that the Parliament itself would be debating the issue, but described Holyrood as ''a fantastic site''.