The police investigation into alleged sexual misconduct by Alex Salmond has widened beyond the civil service, with staff at Edinburgh Airport now involved.

Officers interviewed workers at the airport last week.

The Daily Record reported the police inquiry related to an alleged incident in 2008, when Mr Salmond regularly used the airport as First Minister.

Mr Salmond has denied any misconduct.

No official complaint about Mr Salmond was ever received by the airport’s management.

However Police Scotland spoke to staff after launching an investigation into separate claims made against him by two female civil servants earlier this year.

The two women made formal complaints under a new Scottish Government process in January relating to Mr Salmond’s time in office in 2013.

Mr Salmond, 63, strongly denies any harassment or criminal activity.

He is currently taking legal action against the Government and its top official, Permanent Secretary Leslie Evans, over the handling of the complaints against him.

A spokesman for Edinburgh Airport said: “We can confirm that we are assisting Police Scotland with its enquiries. We cannot comment further at this time.”

Police Scotland said: “Our inquiries continue, we will not be commenting further.”

A spokesman for Mr Salmond said: “Mr Salmond denies all suggestions of misconduct at any time and suggests that everyone should allow police enquires to take their proper course without briefing or breaching their confidentiality.

“Alex has not been interviewed by the police about any matter. He is content to have his case against the Scottish Government stated in the Court of Session in January.”

Mr Salmond started legal action in August, after Ms Evans told him she intended to make a public statement about the complaints against him.

His attempt to stop publicity failed when details emerged in the media regardless.

The government’s most senior law officer, the Lord Advocate James Wolffe QC, advised the matter be referred to the police, who are conducting their own stand-alone probe.

Mr Salmond resigned from the SNP after 45 years as a member, 20 of them as leader.

He has strongly criticised Ms Evans, who has been defended by Nicola Sturgeon.

Backed by £100,000 of donations to a crowdfunder appeal he linked to independence, Mr Salmond is now seeking a judicial review of how the complaint process was conducted.

He claims it was unfair as he was unable to respond properly to the allegations.

At a procedural hearing at the Court of Session last week, his QC, Ronnie Clancy, said one of the two civil servant complaints against him was settled with “finality” in 2013.

This appeared to contradict previous Scottish Government denials that there had been any previous recorded complaints against Mr Salmond.

A substantive judicial review hearing is due to start on January 15 and last four days.