NICOLA Sturgeon’s Government is at the centre of a criminal investigation over the leak of highly sensitive allegations relating to the Alex Salmond sexual misconduct case.

In a letter to the former First Minister’s team, the Information Commissioner’s Office (ICO) wrote that it appears an offence may have been committed over the unauthorised disclosure to a tabloid newspaper.

The correspondence also reveals that Salmond's complaint was passed last year to the ICO’s Criminal Investigations team.

The SNP Government is at loggerheads with the former First Minister over the way civil servants handled complaints about his alleged behaviour when he was in office.

Two women accused Salmond of sexual misconduct, complaints which led to an internal probe followed by a referral to the police.

Salmond, who denies the allegations, successfully challenged the process in court after the Government admitted flaws in the investigation.

The Government breached its own policy after appointing an investigating officer who had previously been in contact with the two women who made the allegations.

After his court victory, Salmond repeated his call for Leslie Evans, the Government’s most senior civil servant, to quit, and he pointedly refused to offer an olive branch to First Minister Nicola Sturgeon.

She and her Government face a raft of inquiries which may focus on the cost of the botched probe as well Sturgeon’s decision to meet Salmond repeatedly during the investigation.

The ICO, which is responsible for looking into data protection breaches, last week confirmed Salmond had “raised a concern” with the watchdog, adding that they are “currently making enquiries with the Scottish government”.

However, details of a letter sent by the ICO in November shows the seriousness of the probe, which relates to a leak to a newspaper about the Salmond case.

The letter states: “From the information provided, it appears that an offence contrary to Section 170 of the [Data Protection] Act may have been committed.”

This part of the legislation creates a criminal offence if a person “knowingly or recklessly” obtains or discloses personal data without the consent of the “data controller”.

Various defences exist, such as if a person charged with an offence proves that the “obtaining, disclosing, procuring or retaining” of the data was necessary for the purposes of preventing or detecting crime. A public interest defence is also enshrined in the statute.

The letter continued: “In these circumstances, the Scottish Government is the data controller of Mr Salmond’s personal data when it is being processed for the purposes of the internal misconduct investigation.

“This complaint has been allocated to the Criminal Investigations team to investigate the subject matter.”

According to the ICO website, this team can carry out search warrants on the premises of suspects to recover evidence during investigations.

The letter added that the watchdog would write to the Government to request any evidence of unlawful disclosures and to identify any person responsible for the alleged data breach.

A source said the fault lay with the leaker, not the newspaper that published the story.

Salmond was incensed by the August leak and accused someone in Government of "sustained leaking" of the "most unfair kind". Allies of Salmond hope the ICO probe will flush out the leaker.

He said in August: “Confidentiality is at the heart of a just procedure and is necessary for both complainers and those complained about. If it is breached, then who is going to complain in future with confidence and how can the person complained about secure any fairness?”

Speaking after last week’s court hearing, the former First Minister returned to the same subjected:

“I’ve been deeply troubled throughout the case by the leaking of confidential information by whoever. Any complaints process has to be transparent, balanced, fair and confidential. That’s in the interests of the complainers and those complained about.”

In another development last week, the Government said it had found no evidence of a data breach relating to the Salmond case.

The Government, following its own internal review, concluded it was "satisfied" that information relating to the case was processed correctly.

An ICO spokesperson said: “Mr Salmond is happy for us to confirm he has raised a concern with the ICO and we are currently making enquiries with the Scottish Government.”

A spokesperson for Salmond said: “There is an ongoing police inquiry and we are making no comment, on or off the record."

A Scottish Government spokesperson said: “This process was ongoing within the Scottish Government for eight months and was kept entirely confidential throughout that period.

“The Scottish Government has never commented on the content of the allegations against Mr Salmond and we will not do so.

“As a precaution and in line with our legal obligations, we instructed a detailed review into our handling of Mr Salmond’s data in August 2018. We are satisfied that information relating to this case has been processed in accordance with our legal and information handling obligations, and that there is no evidence of any data breach.

“We are currently in the process of sharing this information with the Information Commissioner.”

Scottish Tory MSP Annie Wells said: “Once again it looks like the Scottish Government might have made a significant error in the handling of this case. If there has been a data breach here then it reaffirms the utter shambles that they have made of this investigation.

“We can’t lose sight of the fact that the complaints against Alex Salmond by these two women are falling apart because of how poorly this is being handled.”