The probe follows allegations in The Observer newspaper that one of Scotland's largest public relations firms, Beattie Media, touted for business by offering privileged access to Scottish ministers - including Finance Minister Jack McConnell.

BBC Scotland's Chief Political Correspondent John Morrison reports

The company has denied the allegations. However, the activities of its public affairs wing have been suspended pending an internal investigation and it has apologised for any embarrassment caused to the ministers named.

The newspaper's string of allegations include Beattie Media executives telling an undercover reporter, posing as a businessman, that they had access to ministers, most notably Mr McConnell who used to work for a company part owned by Beattie Media.

Scottish Secretary John Reid has defended his son

It also claimed that Scottish Secretary Dr John Reid's son was also implicated in the affair.

Kevin Reid worked for the Labour Party before joining the PR agency to head its political lobbying arm and allegedly boasted about his contacts with the Scottish secretary.

On Sunday, Dr Reid defended his son.

A spokesman for the politician said the newspaper's allegations were laughable and without foundation.

Mr McConnell issued a statement before the paper's publication rubbishing the charges.

It says: "I've become aware of the newspaper linking my previous employment in 1998 with Public Affairs Europe.

"I wish to make clear that neither I nor my staff have regular contact with either of the individuals named in this article or the company as a whole.

"I have not in any way abused my candidacy, my election and my position as a minister.

"In fact, long before the election campaign, I terminated my employment with the PR company.

Jack McConnell used to work for Beattie Media

"I want to make it perfectly clear that any allegation would be totally without foundation, I am therefore writing to request that the standards committee investigate these allegations."

The PR company also defended its position and accused the newspaper of using extreme underhand techniques in an attempt to entrap them.

BBC Scotland's Ruth Wishart interviews Observer journalist Dean Nelson

But the journalist behind the story - The Observer's Scottish Editor Dean Nelson - said there was nothing wrong with the methods used.

He told BBC Radio Scotland: "Beattie Media say they are superior. It has refused to join Scotland's professional association for lobbyists because it believes it doesn't match up to their high standards.

"All we did was to set out to test what they claim."

A spokesman for Mr Dewar said: "The First Minister and all his colleagues are committed to the standards set out in the Ministerial Code of Conduct.

"He expects the same standard from others involved in public life.

"He doesn't believe there's been any breach of the ministerial code but he strongly supports the proposal that the Standards Committee should investigate any allegations made and consider whether there is a need for further investigations in the light of such a report."