The Scottish government is refusing to release the legal advice it received over its Alex Salmond investigation.
A Holyrood committee investigating the handling of harassment complaints against the former first minister requested the information.
However, the Scottish government said it was usual practice to withhold legally privileged material.
Mr Salmond has always denied the harassment claims and was successful in a judicial review.
The Scottish government has published some evidence discussing the judicial review of its investigation of Mr Salmond.
It describes the process leading up to the £512,250 payout to Mr Salmond after his successful legal challenge.
But Alex Cole-Hamilton, a member of the Committee on the Scottish Government Handling of Harassment Complaints, said MSPs should see all the documents.
The Lib Dem MSP said: “This evasiveness on the part of the Scottish government does not serve them, or the people of Scotland, well.
“This saga has already cost the taxpayer more than £500,000. It is a slap in the face to not allow the parliamentary inquiry access to un-redacted versions of these documents.
A spokesman for the Scottish Conservatives said: “This committee is going to be vitally important in scrutinising exactly what went on in this case.
“Transparency is absolutely key to ensuring the wider public know exactly what went on.
“We would hope that will be fully considered by the government in any requests for evidence going forward from the committee.”
In its evidence to the committee, the Scottish government summarised its approach to the judicial review.
It said: “The Scottish government asserts its privilege over all communications it holds about or in relation to legal advice to the Scottish government and litigation involving the Scottish government.
“That is not to say that the Scottish government will not give a full account of its legal position at various points, just that, in accordance with usual practice, it will not disclose the internal processes of taking and receiving advice or the scope and nature of any requests for legal advice or any legal advice provided.”
The evidence said legal action was raised by the former first minister in late August 2018.
The government agreed to settle the case in January 2019 after conceding that the internal investigation into the complaints was “procedurally unfair and tainted by apparent bias”.
Mr Salmond, Nicola Sturgeon and her husband Peter Murrell – the SNP chief executive – are among those listed to appear as witnesses in the committee’s investigation.