SEAWATER infested with possible alien species is to be dumped wholesale by international shipping into Scapa Flow in Orkney creating a potentially catastrophic impact on Scottish wildlife.

The Scottish and UK governments have now been reported to the European Commission for ignoring their environmental advisers over the issue and giving the go ahead to the dumping of seawater from ships in one of Scotland's most precious and historic bays.

Critics fear that allowing oil tankers to discharge their ballast water into Scapa Flow in Orkney could be "catastrophic". The water - used to keep tankers balanced while at sea - is brought in from elsewhere and will cause pollution and introduce invasive alien species that could wreck wildlife and a multi-million pound fishing industry, they say.

Orkney Islands Council, however, insists that there are sufficient safeguards in place to keep Scapa Flow "pristine". Oil tankers began emptying their ballast tanks into the bay earlier this month, as they transfer oil between ships.

Previously, tankers weren't allowed to dump their ballast water in Scapa Flow, but had to do so out at sea. The bay is a 120 square-mile sheltered natural harbour, where the Germans famously scuttled 74 warships in 1919 to avoid them falling into British hands.

Scapa Flow is also linked to the Loch of Stenness, the largest brackish lagoon in the UK. The lagoon is protected under European law as a special area of conservation for its unusual marine life, and is a wintering ground for wildfowl including tufted duck, scaup and goldeneye.

Orkney Council was given the go-ahead by Westminster and Holyrood to change its ballast water regime despite advice from the Scottish Environment Protection Agency (Sepa) that pollution could result. The government's wildlife agency, Scottish Natural Heritage (SNH), also warned of risks to the Loch of Stenness from the accidental introduction of invasive alien species.

Now Steve Sankey, a veteran environmental campaigner who runs a wildlife tourism business in Orkney, has written to the European Commission demanding legal action against the UK and Scottish governments. Scapa Flow is a "sitting duck" for damaging alien species from elsewhere because it has a low tidal flow and is relatively shallow, he argued.

"It's like playing Russian roulette with our inshore fishing and tourism industries which I estimate to be worth a minimum of £50 million to the Orkney economy," he said.

Sankey, who used to be chief executive of the Scottish Wildlife Trust, accused Orkney Council of "hypocrisy on a grand scale" because it was encouraging scores of cruise liners to visit "clean and green" Orkney at the same time as being "hell-bent" on risking the future of Scapa Flow. "They have no concept of sustainable development, and are not fit to be stewards of our environment in general, and Scapa Flow in particular," he said.

His criticisms were echoed by Fiona Matheson, secretary to Orkney Fisheries Association, which represents over 50 fishing vessels and processors. "Where you would expect a local authority to support the indigenous fishing industry, Orkney Council is instead acting competitively against its own people's interests in attempting a rush to the bottom to undercut other ports," she said.

"It is only a matter of time before there is irreversible entry of destructive species to Scapa Flow that will harm the valuable crab and lobster fishery. It brings into question whether the council should be allowed to run commercial enterprises that compete with and threaten to displace local fishermen."

Orkney Islands Council pointed out that tankers had to exchange ballast water three times in the North Sea or the Atlantic before they were allowed to dump it in Scapa Flow. An environmental study for the council concluded that it was "beyond reasonable scientific doubt" that the Loch of Stenness would not be harmed.

"The change to our ballast water policy was not a decision we took lightly and followed comprehensive scientific analysis of the potential impact," said council convener, Steven Heddle.

"This reassured us that tankers can discharge ballast water - a requirement for ship-to-ship transfer operations - in an environmentally responsible manner governed by the strict requirements of our new policy."

He added: "Scapa Flow has been home to a major oil terminal for 40 years and remains a marine environment widely regarded as pristine. It is something we are proud of and determined to maintain."

The UK government's Maritime and Coastguard Agency said it had worked hard to mitigate the perceived risks. "Our assessment is that the likelihood of an incident is very low," said an agency spokesman.

"If such as incident were to occur all the necessary measures are in place to ensure that there would be no adverse effect on the integrity of the environment within Scapa Flow."

According to the Scottish Government, Marine Scotland was still finalising an informal review of the council's decision to approve the new ballast water arrangements.