The Scottish Conservatives have slammed a senior civil servant over a "culture of cover-up" surrounding the true costs of the Holyrood building project.

Tory leader David McLetchie led the attack after it emerged that the Holyrood building project costs had soared to £420 million.

Giving evidence to the Fraser inquiry, site controller Hugh Fisher revealed that he had been told that the real costs could not be made public for political reasons.

He named project chief Barbara Doig, a civil servant, as the figure who attempted to keep the escalating costs out of the public domain.

The Holyrood project, which was initially predicted to cost £50 million, now appears set to cost the Scottish taxpayer at least £420 million - some £20 million more than the most recent estimate.

The Tories said ministers had to explain what went on when Donald Dewar was in control of the Scottish parliament project.

"It is not for Barbara Doig... to decide what is or is not 'politically appropriate'. This shows that she and Donald Dewar were at the centre of a culture of cover-up and secrecy that has bedevilled this project from day one," said McLetchie.