The National Assembly might have to pay millions in compensation if the planned new debating chamber in Cardiff Bay does not go ahead.

First Secretary Rhodri Morgan called a temporary halt to the project on Wednesday saying he wanted to review the cost implications.

But the Royal Institute of British Architects has said that if the waterfront project is cancelled there could be substantial penalty clauses.

The future of the new �23m Welsh Assembly building was thrown into turmoil after the project was put on hold.

Work was expected to start on the building in November and it was hoped it would be completed by May 2002 and be fully operational three months later.

Mr Morgan, though, told AMs that he wanted to thoroughly review the whole project.

He said he was making the decision immediately so as not to trigger further significant expenditure and make it more difficult to consider at a future date.

Ian Salisbury of RIBA said: "If a large contract such as this is cancelled there's a significant probability that the contract will contain provisions for wasted costs of a substantial amount."

An Assembly spokesman refused to comment on how much would have to be paid out if the new building did not go ahead.

He said it was far too early to speculate as the project was only on temporary hold.

A National Audit Office report on the Assembly's accommodation needs is due to be published in June.

The First Secretary said that he realised the decision to delay the project would "disappoint many people in the chamber".

"I have not reached this decision lightly, but it is clearly a matter of public interest and it is important that we get it right," he said.

Three options

He said there are three options - the temporary home becomes permanent, the Assembly goes to other premises in Cardiff or the plan for the new chamber gets the go-ahead

The new building - designed by the Richard Rogers Partnership - will house a debating chamber, committee rooms and offices.

It is due to be built adjacent to the Assembly's current temporary home in a converted office block in Cardiff Bay.

It was hoped that Cardiff's historic City Hall would be chosen over other rival sites.

Discussions between former Welsh Secretary Ron Davies and Cardiff Council leader Russell Goodway broke down over the asking price for the building.

It was decided to invite designs for a new building in the Welsh capital.