Greenbelt Group Ltd was given £170,375 to look after the Black Cart Water estate next to Glasgow Airport in 2002, but conservation groups tasked with monitoring the land have expressed “extreme concern” that the money was never spent on its intended purpose.

Both the RSPB and Scottish Natural Heritage (SNH), the government agency responsible for the nation’s wildlife, said they saw little evidence that the 25-hectare site was being adequately maintained, and the current owner of the land also spoke of his concerns.

Six years after the payment of £145,000 plus VAT was received from Scottish Enterprise, Glasgow-based Greenbelt sold a chunk of the estate to a farmer, pocketing a further £30,000.

The land’s new owner is left to care for the conservation area, which is doubly protected as a Site of Special Scientific Interest (SSSI) and an EU-recognised wild bird protection area, and he said that he was never made aware of any grant money for maintenance.

SNH warned that he is unlikely to get any financial help as it would be considered “double funding” given that a large grant has already been made for the site, which is one of Europe’s most important whooper swan habitats.

Dave Lang, SNH conservation officer for Strathclyde and Ayrshire, said: “It’s very difficult to identify what management they’ve implemented, and yet there’s a fairly large sum of public money handed to them. It certainly doesn’t seem to have been spent on what it was meant to be. There’s nothing tangible been done for these swans, or very little.”

Scottish Ornithologists’ Club representative Iain Gibson, who has worked with Greenbelt on the site for more than a decade, said he was “shocked” by recent developments.

“Greenbelt never made it clear to me that they had been given a sum upfront. I’m not saying they’ve done anything illegal, but who knows where that money has gone?

“I’ve been working closely with them since day one, and I’d estimate that only £10,000 to £20,000 of the work that was planned has been done. For most of the past decade they neglected the site significantly,” he said.

The Black Cart flood plain lies between Glasgow Airport and Inchinnan Business Park, which is also managed by Greenbelt Group as part of their £170,000 deal with Scottish Enterprise. Permission for the business park was granted in 1999 only on condition the SSSI site was managed “so as to ensure the continued habitat suitable for the flock of whooper swans which frequent this area”.

Toby Wilson from the RSPB described the whooper swans as an “internationally important” flock that travelled 800 miles to migrate to the Black Cart site every year, adding that it was “crucial that their chosen habitat is in the best possible condition for them”.

He said after the award of the Scottish Enterprise money in 2002, “a plan was drawn up and money put aside but, seven years later, RSPB Scotland is extremely concerned that management still does not appear to have taken place”.

Robert Gatherer, the farmer who purchased the land with his brother to graze the family’s cattle, said he was left wondering “what had happened” to the Scottish Enterprise funding, adding: “There’s a lot of people making a lot of money here, and we’re not any of them.” Mr Gatherer said the land was “a pure mess the way it was left” when he bought it. “We’re trying to tidy it up now. There were old fences lying flat, and they were no use to cattle or the swans,” he added.

Greenbelt Group has its beginnings in a public body set up in 1992 by SNH, Scottish Enterprise Network and Strathclyde Regional Council for land management. It was reorganised as a standalone company in 1999, and there has been no public sector interest since 2004.

Greenbelt managing director Alex Middleton said the SSSI site had been “managed sympathetically” in conjunction with SNH and the RSPB “as both organisations know”. Mr Middleton said his firm had provided “a specialist grazing regime” for 12 years in accordance with the demands of their agreement with Scottish Enterprise, and that he was not aware of any complaints from the conservation organisations.

The SSSI area was ancillary to the main land of the Inchinnan Business Park, he added, and the £170,000 of public funding was intended for maintaining the business park over and above the whooper swan reserve.

Mr Middleton said that the RSPB and Scottish Enterprise were kept “fully informed” of the proposal to sell the land to Mr Gatherer, and that the new owner had been “fully aware” of the SSSI designation and associated responsibilities.

Scottish Enterprise said that while it had a right of pre-emption on the sale of the land last year, buying it from Greenbelt would “not have been the best use of public money”.