Scientists say that the evidence contained in a series of reports running into hundreds of pages contradicts ministerial assurances that the effects of the pollution are "insignificant". But the Government refuses to publish them.
The refusal, scientists say, is part of an astonishing catalogue of concealment and lax enforcement by the Department of Trade and Industry, which is responsible both for policing pollution from oil installations - and for promoting the industry's expansion.
The department keeps no records of oil spills or excessive pollution by individual companies, and refuses to supply measurements of specific discharges. Such information is freely published for the Norwegian part of the North Sea, however, and available on land-based polluters throughout Britain.
The DTI cannot say how many environmental inspections it has carried out and keeps no records of these either. Until two years ago, it had only one part-time inspector to cover all the British offshore industry's 200 or so structures, and only once in 25 years has it prosecuted a company for pollution.
Britain's oil installations cause much more contamination than those elsewhere in the North Sea. Earlier this year, a Dutch study concluded: "The amount of oil discharged in the UK sector is many times higher than in the other sectors."
Scientists at Oslo University say that between 1990 and 1995, British rigs produced more than eight times as much pollution while drilling as Norwegian ones, and that the gap will now be even greater, as only the UK still permits discharge of the most damaging oil-based muds - used to lubricate the drills - into the sea.
Work by Professor John Gray, a British marine biologist at the university, shows that the muds have affected 10 times as great an area around Norwegian rigs as had been predicted, and that the areas of damage around individual installations and fields were beginning to merge.
Marine life such as the burrowing brittle star, which is food for many fish, had been obliterated near platforms. The sea's threatened fish stocks could be even further depleted.
Professor Gray says this is likely to be even worse in British waters where the pollution is so much greater. He says that surveys carried out by oil companies and submitted to the Government, have shown serious damage but have been kept confidential. Scientists who have analysed them have not been allowed to publish the data. The department says it has studies on the effects of drilling on the sea bed, running into "hundreds of pages". They were "not in publishable form". Last month Lord Fraser of Carmyllie, the energy minister at the department, described Britain's North Sea oil and gas industry as "an insignificant source of pollution".
The Government's lackadaisical policing has been exposed by attempts by a small environmental group, the Marine Conservation Society, to obtain material from the department under EU freedom of information legislation. The group asked repeatedly this summer for details on oil spills and breaches of pollution regulations, and on inspections of offshore installations. The department initially said it was "impractical" to give the information but replied more fully after being reminded it was in breach of EU law.
Its reply revealed that:
n It had no record of "individual breaches" of pollution regulations.
n Records of oil spills were only held "for a time" and not kept "on a company basis".
n There was "no record of offshore environmental inspections previously undertaken".
n Up to the end of 1989, there were only two part-time environmental inspectors. Between 1990 and 1995 there was only one, also part-time. It was "unclear how much of their time was spent on inspections". Now they had been increased to six, but some "combined their work with other activities".
n Inspectors "rely on the oil and gas industry" to take them to installations which makes it "impractical to make a totally unannounced visit".
The department told the conservation group that it would only be able to supply even limited information at a charge of "in the order of pounds 4,300" - although EU law stipulates it should be given at "reasonable cost".
This situation contrasts with the United States which has 60 offshore oil inspectors making up to 160 checks per platform each year, and Norway, which publishes detailed figures on pollution from each installation. In Britain the Environment Agency maintains public registers of discharges to air and water by land-based polluters, which can be examined free of charge.
Mr Guy Linley-Adams, director of conservation at the society said last night: "To have no record of breaches of pollution regulations is quite staggering. To refuse to name companies causing oil spills is outrageous and probably illegal. This is the most amazing way to regulate a massive industry operating in the highly sensitive marine environment."Reuse content