Jack McConnell has defended his decision to establish an independent inquiry into the soaring costs of the Holyrood building project.

The first minister said the inquiry, to be headed by Lord Fraser of Carmyllie, would provide answers to the key questions.

The probe comes amid predictions that the new parliament could cost over £400 million - 10 times the initial estimate.

McConnell said the inquiry would examine the period before the 1999 election and insisted it would "get to the heart of the matter".

"Nothing that the government or parliament has done, either before or after devolution, will be beyond the scrutiny of the investigation," he said.

"I consider that an independent investigation into the escalating costs and construction delays associated with the new parliament building should be initiated because this, more than any other issue, overshadows the many real achievements of our young parliament.

"The investigation will produce a full account of the key decisions and factors that have determined the cost and value of the parliament throughout the life of the project."

In a statement to MSPs McConnell vowed to hand over any documents demanded by the former Scottish lord advocate.

Critics say that Donald Dewar, who was Scottish secretary prior to devolution, deliberately underestimated the cost of the building to win support for the project.

At Westminster the SNP has accused the government of mishandling the project in its early stages.

The party has tabled a series of questions demanding to know why the initial cost predictions were so far short of the reality.

"Westminster is responsible for all of the key decisions about the Holyrood project - the site, the design, and the open-ended contractual arrangements - and they were all wrong," said the party's chief whip, Pete Wishart.

"It is high time that responsibility for the Holyrood fiasco was allocated where it belongs - fairly and squarely with Labour at Westminster, and that is what my questions are seeking to do."