Conservationists hope a Highland court case could lift the threat of nine million tonnes of crude oil being transferred between tankers lying near precious environmental sites in waters where dolphins swim.

But the litigation against the Cromarty Firth Port Authority (CFPA) could also have serious impact on some of the busiest ports, including Aberdeen, if their systems of governance are found to have been improperly established in law.

The case is being taken by the former owner of the Invergordon-based Port Services Ltd (PSL) Wendy Clark. It was wrongly reported to have failed at the Court of Session, but in fact was sent down to Tain Sheriff Court in Easter Ross for continued hearing.

This follows the Scottish Civil Courts Reform into court procedures in Scotland which recommended any case for damages of less than £100,000, should be heard in the local sheriff court first. However according to Wendy Clark, it may yet return to the highest civil court in Edinburgh.

The case centres on a rent bond of £1m, which the CFPA had demanded from PSL before agreeing to lease them space at Invergordon. This had seriously affected the company’s finances, Mrs Clark explained:

“The basis of our litigation is the port authority hadn’t asked for similar rent bonds from other tenants. We don’t believe the legislation which set up the port authority gave it powers to extract such a rent bond. Thirdly we are advised by our QC that the constitution of the board of the port authority is incompetent in law.

“Counsel’s opinion is clear that the port authority was acting ‘ ultra vires’ beyond its legal power or authority, so there is no time limit to a legal challenge.”

At issue is who appointed the CFPA’s board of directors. Under the 1973 act which set up trust ports like the Cromarty Firth, it was always understood that the responsible minister would oversee and approve the appointment of directors to the boards, Mrs Clark said.

“However when we have learnt that something called ‘a confirmation order’ was drafted by the port authority. In 2003 after the Scottish Parliament was established the then transport minister was handed this confirmation order. He signed it off without it being debated by MSPs. So you effectively had a port authority amending a Westminster Act.

“If a court finds that the CFPA did indeed act ‘ultra vires’, it would call into question all the decisions the directors have taken since, including their controversial decision to apply for a licence to conduct ship to ship oil transfers.

“Indeed we understand that the Cromarty Firth Port Authority then went out an advised some other trust ports to frame their own confirmation orders. In particular Aberdeen, Montrose and Peterhead, who could also be affected. ”

A CFPA spokeswoman said “We can confirm that this matter continues to be subject to legal proceedings. As such, we’re unable to comment further.” Transport Scotland, for the Scottish Government, also refused to comment because of the impending case at Tain.

A spokeswoman for Aberdeen Harbour said Aberdeen Harbour was a Trust Port and operated in accordance with Transport Scotland’s ‘Modern Trust Ports for Scotland, Guidance for good governance’

But John Finnie the Highlands and Islands Green Party MSP has called on the Maritime and Coastguard Agency to delay any decision on the CFPA for ship to ship transfers until this case is resolved, however long it takes.