Scottish politicians say judges should be issued with new guidance after millionaire bus magnate Ann Gloag won her case to ban the public from her land.

Campaigners say the ruling, by Sheriff Michael Fletcher, blows a massive hole in Scotland’s right-to-roam legislation and could lead to landowners across the country closing their estates.

MSP Rosanna Cunningham, whose Perth constituency covers Mrs Gloag’s Kinfauns Castle estate from which walkers, runners and cyclists are now excluded, will raise the matter tomorrow during First Minister’s Questions in the Holyrood parliament. She says she does not believe it was necessary to ban the public from such a large area of her estate.

Rhona Brankin, Labour’s environment spokesman in the Scots parliament, said the ruling was extremely disappointing and accused Sheriff Fletcher of ignoring the provisions of the Scottish Outdoor Access Code which formed part of the Land Reform (Scotland) Act. The act introduced a legal right to roam. She said: “If the spirit of that bill [the Land Reform Bill] is not being respected, then we need to take responsible steps to remedy that.”

She said Labour would be calling for a review of the Act to see how much Sheriff Fletcher’s judgement undermined it.

The Ramblers’ Association in Scotland said it was considering action to have the ruling overturned. In a statement, the association said: “We are disappointed by this court decision. Our Scottish Committee will study the judgement and, following legal advice, will decide whether to appeal the decision.

“It does not appear to us that this judgement properly reflects the intentions of the Scottish Parliament when it passed the Land Reform (Scotland) Act 2003. We are surprised that the Sheriff takes little account of the Scottish Outdoor Access Code, suggesting that the section of the code which deals with privacy issues in relation to large houses in the countryside is not of ‘direct help’ in this case.

“We recognise that there are important privacy and security issues at Kinfauns but do not think these have been resolved through this court action. We regret that the dispute arose when Mrs Gloag erected a mile long security fence around her property, without first obtaining the necessary planning approval. There is a serious risk that this court judgement could encourage other landowners to take similar action to exclude public access from extensive tracts of ground.

“If this were to happen it could fundamentally undermine the intentions of the land reform legislation.”

First Minister Alex Salmond’s office said the executive would study the judgement before deciding on any action.

Sheriff Michael Fletcher, in delivering his decision, said the ‘nature of the building and its prominence’ meant a larger section of surrounding land was required by Mrs Gloag to ensure her family’s privacy and enjoyment of her home.

He said it falls under Section 6 of the Land Reform Act: land which is exempt for reasons of privacy or enjoyment by the owner.

In passing judgement, he said: “Helpful though the provisions [of the Act] are, they are extremely general and no help is given as to what is meant for instance by ‘other characteristics’.”

“[Kinfauns Castle] is of a substantial size, being one of the larger country mansion houses in Perthshire and indeed probably in Scotland. It is of a very substantial value such that only a small number of persons would be able to afford to own it and run it as a private house.

“The nature of the building and its prominence would point to a larger rather than smaller area of ground being required to be sufficient for the purposes of Section 6 of the act.”

Denis Canavan, president of the Ramblers’ Association in Scotland, said the judgement implied that the bigger someone’s house, the more land was needed to ensure the owner’s privacy. He said the verdict flouted the will of the Scottish Parliament.

Legal commentators say the case may well end up in the House of Lords.

A spokesman for Ann Gloag said: “We are delighted that the sheriff has recognised the importance of the right for everyone in Scotland to enjoy reasonable privacy within their own homes.”

Retrospective planning permission was granted to Mrs Gloag for a two-metre-high fence erected around the disputed area of her estate. Perth and Kinross Council then told her that the land within the fence was subject to the access provisions of the Land Reform (Scotland) Act. Her successful appeal against that ruling came this week, as she received a CBI award for businesswomen. She is rated one of the richest women in Britain, with a fortune estimated at almost £400m. She bought Kinfauns in 2005 for £4m. She and her brother Brian Souter made their fortune with the Stagecoach bus company.

Labour donor Euan Snowie has launched a similar appeal against an access ruling at his Stirlingshire estate. Judgement in that case is expected in the autumn.