OIL exploration north-west of Scotland is threatening a coral reef which has survived in an area considered to be among the coldest and most barren on earth, marine biologists will be told today.

Some scientists believe the reef, some of which may date from the Ice Age, could emerge as the most important eco-system in the northern Atlantic, supporting up to 800 species of fish and marine animal. It was built by the cold water coral polyp, Lophelia pertusa.

But the area is being scoured by most of the world's big oil companies, which believe it has reserves in excess of 1.2 billion tonnes - greater than those of the North Sea. BP is to start producing from the first field in the area, Foinaven, this year.

Marine biologists attending the Greenpeace conference at London university today will urge the Government to stop exploration until the impact on the coral and other marine life has been evaluated.

Greenpeace believes the oil exploration licences issued in April last year are illegal, and has already lodged a complaint in the European Court. Further action is planned in British courts to force ministers to order an environmental impact assessment on the site.

Research into the coral, funded by the Government and the oil industry, is under way, but scientists involved argue that no exploration should be permitted until the results are available, which could be more than a year off.

They warn the coral could be smothered by clouds of sediment kicked up by drilling, and may also be vulnerable to chemical contamination from oil wells.

Alex Rogers of the Marine Biological Association said: "We have really been taken by surprise by the extent to which it is distributed and by the diversity of life it supports."