Scotland's Freedom of Information legislation is "in danger of being eroded" as arm's-length public-sector bodies dodge transparency.

That is the claim of the group that helped bring the law to the statute books 14 years ago and which has been watching its implementation ever since.

The Campaign for Freedom of Information in Scotland (CFoIS) fears a proliferation of hybrid organisations delivering public services poses a threat to the spirit of the law.

Carole Ewart, its convener, said: "While Scotland hasn’t seen the up-front challenge to our information rights that has recently been fought off at UK-level, the consistent failure of Scotland’s governments ensure information rights are maintained when public services are hived-off to arms-length bodies, housing associations, PPP’s or NPD Trusts, or private companies, has meant an erosion of people’s right to ask for information."

CFoIS has launched a manifesto ahead of next month's Holyrood elections. Its key demand is for an audit of all Arm's-Length External Organisations (ALEOs) and for them to be drawn into the FoI net quickly, and for the law to be changed so that coverage details the public functions to be covered, as well as listing the public bodies.

Ms Ewart said: "It is amazing that we still have no idea how many ALEOs exist in Scotland. A recent Scottish Local Government Committee report into them failed to even mention the issue of information rights.

"We need to ensure that FoI follows the public pound.”

CFoIS manifest also warns of a "two-tier system" on FoI. There is a suggestion that grant-aided independent special schools be given longer to respond to FoI requests than council ones. Ms Ewart said this was a breach of a ‘universal’ rights.

She said: "To make people wait so much longer for their information will cause problems for individual requesters but we are concerned about the wider detriment if other public service providers – like housing associations, private companies or third sector providers start demanding special treatment too.

"Independent polling proves Freedom of Information is widely known and backed by the Scottish public. It is an enforceable right that should be maintained."