A further challenge is to be made to release the correspondence behind the knighthood of Sir Brian Souter, who donated £1 million in an effort to keep Section 28 on the statute books.

Sir Brian funded an unsuccessful Keep the Clause campaign in 2000 to maintain Section 2A of the Local Government Act 1986 which banned the “promotion of homosexuality” and the teaching of the “acceptability of homosexuality as a pretended family relationship”.

Announcements last year said the Stagecoach tycoon was to be honoured for his services to transport and the voluntary sector. Sir Brian’s charitable trust has given away £20m since 1992.

The Cabinet Office, however, refused to give further details of the nomination for a knighthood. The government in Scotland has similarly refused to release any correspondence with or about the transport millionaire, who is a major donor to the Scottish National Party, before his knighthood.

Last year, he personally pledged to match donations to the party up to £500,000 before it was returned to office in the ensuing election.

The Scottish Daily Record reports that a Labour researcher was told the cost of finding the paperwork would exceed the £600 limit on information requests.

Ross Gilligan said: “I now plan to make a substantive appeal. I find it utterly implausible that finding this information could cost over £600.”

Jackson Carlaw, deputy leader of the Scottish Conservatives added: “Alex Salmond is certainly acting like a man with something to hide.”

Willie Rennie, leader of the Scottish Liberal Democrats said: “This is getting more suspicious by the day.”

The paper said Mr Gilligan’s first two requests have been denied firstly because Buckingham Palace did not want the information made public and secondly because his request was not clear.

The issue has been raised as the debate over whether to allow gay couples to marry in Scotland continues, a move which has been approved by the Scottish National Party leader Alex Salmond.

A government spokesperson said Sir Brian had had no contact with First Minister Salmond on that issue and that correspondence in the lead-up to his nomination for a knighthood would be too wide-ranging and expensive to track down. The government also denied that Sir Brian’s donations had any influence on public transport policy.

Sir Brian’s office declined to comment to the Scottish Daily Record and to PinkNews.co.uk today.