Scotland’s Deputy First Minister has been accused of “unacceptable” obstruction of the Alex Salmond inquiry after refusing to allow two Government witnesses to give evidence.

John Swinney has blocked two witnesses from appearing next week before the Holyrood committee probing the Government’s botched investigation of sexual harassment allegations against the former first minister, provoking further ire from MSPs.

The committee had wanted to question Judith Mackinnon, the investigating officer whose prior contact with two of Mr Salmond’s accusers caused the Government investigation to be ruled “unlawful” and “tainted with apparent bias”.

Ms Mackinnon has previously appeared virtually before the committee but the Scottish Government requested that only the audio evidence was available to the public.

This ham-fisted political interference into the work of this committee is simply unacceptable

The committee had also asked the Government’s workforce director, Gillian Russell, to give evidence on Tuesday.

But Mr Swinney has written to the committee to refuse the requests, claiming it could create an “unacceptable risk” of potential identification of complainers in the court case against Mr Salmond.

Mr Salmond was acquitted of 13 charges at the High Court in Edinburgh in March.

The court case followed a legal battle in which he was awarded more than £500,000 when the Court of Session in Edinburgh ruled a Scottish Government investigation into his conduct was unlawful.

The Deputy First Minister said the Government is still attempting to agree with Mr Salmond’s lawyers what evidence can be released, so cannot provide “uncontested documents, a timeline and a statement” about the Government’s handling of the complaints.

In a letter to the committee, Mr Swinney argued allowing the witnesses to give either written or oral evidence could “inadvertently breach either the undertaking or the court order preventing jigsaw identification of the complainers”.

Mr Swinney wrote: “Having carefully considered the balance of those risks and the other possible mitigation that could be put in place with the requirement to comply with the committee’s legitimate request to take evidence from these witnesses, I have concluded that agreeing to these witnesses appearing on November 24 would create an unacceptable risk and therefore I cannot agree to the committee’s request.”

He added that he will consider whether to allow the witnesses to appear in future if an agreement is reached with Mr Salmond’s legal team.

In reply, committee convener Linda Fabiani said: “I find it unacceptable that you are now writing to the committee to say that the Scottish Government does not agree to two of its civil servants giving evidence to the committee at its meeting next Tuesday because the Scottish Government has not produced a timeline and statement to accompany documentation.

“While the committee appreciates that no witness should be put in a position where they might inadvertently breach a court undertaking or court order, it is the Scottish Government which has put its own employees in this position.”

The SNP MSP again stressed that the committee is not asking for any documents that would require permission from a court to release, and said she previously warned the failure to provide the documents “was likely to mean that Scottish Government officials would need to spend more time in Committee covering matters in person that should have been covered by the Scottish Government’s written statement and associated documentation”.

Scottish Labour deputy leader and committee member Jackie Baillie said: “This is nothing short of an outrage.

“This ham-fisted political interference into the work of this committee is simply unacceptable.

“The secrecy and obfuscation of the Scottish Government knows no bounds.

“The worst of this latest episode is that John Swinney is blaming the lack of written evidence for the non-appearance of these witnesses, when he is the one that is withholding the evidence. You really couldn’t make it up.

“The First Minister’s commitment to allow the committee access to all documents and personnel it may need was clearly nothing more than a bad joke.

“The committee must resist this political interference and redouble its efforts to uncovering the truth at the heart of this sordid affair.”

Scottish Conservative committee member Murdo Fraser said: “This is yet further confirmation that the SNP Government are doing everything they can to shut down this inquiry.

“They continue to block the vital work of this committee at every turn and are evading any sort of scrutiny.

“The public deserve to know why £500,000 of their money was wasted but the idea of being transparent is completely non-existent at the heart of this SNP Government.”