SCOTLAND’S official environmental watchdog has lodged an objection to plans for the transfer of nearly nine million tonnes of crude oil a year between tankers at the mouth of the Cromarty Firth.

The Scottish Environment Protection Agency said it was a “holding objection” for the moment as it tries to resolve difficulties with the Cromarty Firth Port Authority’s application to undertake the lucrative ship-to-ship transfers.

It follows Scottish Natural Heritage also raising concerns about the plan because of the impact of even a small oil spill on the Moray Firth dolphins, designated environmental sites and bird sanctuaries.

Environment Secretary Richard Lochhead has said he would pay particular attention to what the two organisations say.

Ship-to-ship transfers have been conducted safely for many years at the nearby Nigg oil terminal, where tankers lie alongside each other, secured to the jetty.

It is still available and there are local suspicions that recent strained relations between Nigg’s owners Global Energy and the port authority have influenced the latter’s future strategy.

The Scottish Environment Protection Agency (Sepa) warns in its submission to the Maritime and Coastguard Agency, which is considering the licence application, that transferring oil at sea as the port authority is proposing, poses a greater threat.

It said: “Sepa note the port authority’s strong track record in prevention of oil spills although it would appear that these are related to dockside transfers rather than open sea ship to ship transfers.

"Open sea transfers would seem to present more risk and greater difficulty in containing any oil spillage. Oil spill prevention is essential in a sensitive area such as the Cromarty Firth."

The port authority’s modelling was based on just one tonne of oil escaping during the transfer of 180,000 tonnes between vessels in each session, four times a month.

Sepa said there were doubts this was a "realistic scenario”. Quoted rates are two tonnes of oil per second and tanker transfer pumps could not be switched off immediately but would require to be gradually slowed down for safety reasons, Sepa said.

The agency has asked the port authority to respond to the submission that an oil spill of 300 tonnes should be the worst case scenario, as this is a requirement of the ship-to-ship transfer regulations.

Sepa also questioned why the modelling used only high tide as a starting point. This would have the effect of keeping an oil spill out of the Cromarty Firth, as the falling tide would push water out of the area.

“It would seem appropriate to have run some models based on an incoming tide when oil would be swept in," it said. "This would also be applicable to the modelling of ballast water discharges.

Sepa said an oil spill could have “potentially serious consequences for sensitive habitats, nationally important species and economic activities in the area that depend upon the water environment". "The costs involved in mitigation, clean up, habitat recovery and compensation could be huge," it added.

RSPB Scotland, the Scottish Wildlife Trust and the National Trust for Scotland, have all objected, as has Cromarty and District Community Council. More than 6,000 people have signed two petitions opposing the plan.

However Bob Buskie, chief executive officer of the port authority, said: “We are encouraged by the responses we’ve received as part of this stage of the consultation process and will work closely with all stakeholders to address their feedback and any concerns raised.

"Worldwide it is estimated that between 8-10,000 ship-to-ship operations are carried out every year.

"The port itself has undertaken this activity for years safely and without incident. As part of our legal responsibility to safeguard the environment of the Firth we have strict procedures in place to ensure that the operation does not go ahead unless all requirements and conditions are met.

"The current oil spill contingency plan was approved last year by the MCA following a period of consultation with Marine Scotland, SNH, Highland Council and Sepa.”