The new Scottish Parliament building may not be finished on time due to the installation of bomb-proof , MSPs have been warned.

Project director Sarah Davidson admitted that there was fresh "uncertainty" over the completion date for the Holyrood project.

She was speaking to the parliament's finance committee, where discussions also sparked a row over increased bomb-proofing measures.

It's fair to say there is still a degree of uncertainty

Sarah Davidson Project director

These steps, which were introduced in the wake of the 11 September attacks on the United States, are being blamed for the cost of the project breaking through the �300m barrier.

The cost was defended by Liberal Democrat MSP Robert Brown, a member of the Scottish Parliamentary Corporate Body (SPCB).

He told the committee: "The SPCB fully understand the cost issue, but there's also increasing recognition that the parliament is likely to be a world class building that will be a centrepiece for the evolving democracy in Scotland."

It was planned that the structure would be officially handed over to officials next May, with MSPs moving in from next September.

Behind schedule

However, Ms Davidson said on Tuesday that she could not guarantee that the project would be completed by the target date because of complex glazing work.

She said that Bovis Len Lease, the firm in charge of the project, was "concerned" that glazing contractors Mero had fallen behind schedule.

"The last firm projection we had on the table from the construction manager was envisaging the building being handed over in April/May with occupation by the parliament in September," said Ms Davidson.

Work is continuing on the project

"It's been reported to us that most of the dates from Mero do comply, but there are one or two others that Bovis are concerned about.

"It's fair to say there is still a degree of uncertainty around that because there are a few outstanding dates, but once there's more certainty we will report back to the committee."

Meanwhile, Scottish National Party MSP Fergus Ewing was accused of making "tasteless" comments over the need for bomb-proofing measures.

He said: "What sort of bomb are we going to be protected against?

"How on earth can you protect a building against an extremely powerful, say nuclear, bomb?

Safety advice

"Are we not throwing away �20-30m? The public just can't understand this."

Labour MSP Tom McCabe said it would have been "irresponsible" to ignore safety advice.

Liberal Democrat MSP Jamie Stone later said the comments were "singularly tasteless" in the light of 11 September.

"What sort of message does that send out to staff and visitors to the building?" he asked.