A reporter appointed by the Scottish Government has accused Dumfries & Galloway Council of "acting in an unreasonable manner" after councillors used a routine planning procedure to derail a £40 million, 250-job data-farm project.

Reporter Lance Guilford last week reversed the council's August 2013 refusal of an extension to a three-year-old permission for ScotiaGlobal to build Europe's first large-scale modular or "build-as-you-grow" data farm at Johnstonebank near Ecclefechan. However, company sources claim the five-month delay and uncertainty has lost the project to Scotland.

Last year's decision by a 9-7 vote, led by Archie Dryburgh, a Unite official and Labour candidate for the neighbouring Dumfriesshire, Clydesdale and Tweeddale Westminster seat, was made in defiance of advice from officials. Perceived as damaging the long-term prospects of attracting investment to one of Scotland's most fragile rural economies, the ruling has since been criticised by the local chamber of commerce and by Scottish Enterprise (SE), which has worked to bring large-scale data handling to the area for seven years.

SE, with consultants Hurley Palmer Flatt, identified the Johnstonebank site as the second-best site in Scotland to host a large-scale data farm, with the potential to kick-start a major new Scottish industry.

In his decision notices of January 6, Guilford wrote that the extension application process should not have questioned the principle of the ­development, but instead considered whether there had been "a material change in circumstances since the original planning permission in principle which could justify the refusal of planing permission and whether there is likely to be continued failure to begin the development". The answer to both, he said, was no.

Referring to the SE survey, written six months before the planning hearing, he said: "This recent report constitutes a change in circumstances but one which favours continued support for the proposed development."

He ruled against the award of expenses to ScotiaGlobal on the grounds that the judgment has "not resulted in significant additional expense on behalf of the appellant".

"I find that the council has in part acted in an unreasonable manner in the determination of the planning application relating to the appeal."

ScotiaGlobal wanted to build the datacentre in partnership with the French multinational APC Schneider. Prior to the reporter's ruling ScotiaGlobal submitted a complaint against Councillor Dryburgh to the Standards Commissioner, accusing him of a mounting campaign against the project based on his support for another, similar data-farm project whose similar application for an extension of planning permission was granted a month after the surprise decision on the Ecclefechan site. The two sites are not perceived to be rivals.

ScotiaGlobal seized on the reporter's identification of the Scottish Enterprise report as a material consideration in favour of the project to ask why Dumfries and Galloway, whose head of planning Steve Rogers received the SE report in June, did not circulate it to planning committee colleagues, especially given the rarity of major ­developments in the region.

Dryburgh has since claimed that he was unaware of the existence of the report, whose list of points in favour of the site directly contradicts the objections he has raised against the project.

The report was sent to local politicians, including Dryburgh's Dumfriesshire Labour Party colleague, Dr Elaine Murray MSP.

Murray, who was previously supportive of the project, told the Sunday Herald: "Councillor Dryburgh and I do not share an office, and there is no obligation on me to pass a document from a third party to others including Labour councillors.

"I would be contravening planning legislation if I tried to influence members of the planning applications committee for or against an application. Surely the onus to bring this report to the attention of the planning committee rests with the applicants and not with anyone else who may have received a copy of the report?"

The 22-page complaint ­document includes allegations that Dryburgh pressurised council officials to provide a reason for refusing the application and, by advocating another project during consideration of Johnstonebank, breached his duty of impartiality.

A spokesman for Dumfries & Galloway Council declined to comment on the Reporter's ruling.