THE official guardians of Scotland’s wildlife fear even the smallest spill from planned ship-to-ship oil transfers could pose a significant threat to protected dolphins.

Scottish Natural Heritage (SNH) also highlighted the danger of pollution to environmental sites and bird sanctuaries near the Cromarty Firth.

The area's port authority (CFPA) has applied for a licence to conduct the crude oil transfers between tankers anchored at sea.

Some 180,000 tonnes would be transferred four times a month to a maximum of 8,640,000 tonnes a year.

The plan has outraged local people and environmentalists, who say there is no need as oil transfers have been conducted safely at the nearby Nigg facility’s jetty for many years.

Steve North, operations manager from SNH said the agency agreed with CFPA’s environmental statement identifying the key issues as the risks posed from oil pollution, ballast water discharges, increased shipping movement and underwater noise.

“However we do not agree with the conclusion of the environmental statement that there will be no likely significant effect on European designated sites, so we have advised the MCA that further assessment is required.

“Whilst we consider that mitigation can reduce adverse effects, we do not think that the risks can be eliminated altogether. Risks to the bottlenose dolphins are particularly significant. The entrance to the Cromarty Firth is extremely important to the dolphins and a large proportion of the local population use these waters all year. Even small oil spills could have a significant effect on them.”

He said SNH had not officially objected but the UK Maritime and Coastguard Agency (MCA) was required to take its advice into account.

However RSPB Scotland, the Scottish Wildlife Trust and the National Trust for Scotland, have all objected, and more than 6,000 people have signed two petitions opposing the plan.

But Bob Buskie, the CEO of the port authority, said: “We fully understand SNH’s concerns which the port will now discuss and take forward with the MCA.

"We have to stress the port takes its environmental responsibilities extremely seriously, in fact the port has a legal responsibility to safeguard the environment of the Firth. “

He said the current oil spill contingency plan had been approved last year by the MCA following a period of consultation with Marine Scotland, SNH, Highland Council and SEPA.

An MCA spokeswoman said: application. We will continue to engage with relevant stakeholders, including the Scottish Government, before any decision is made.”