Serious spills of oil and gas from North Sea platforms are occurring at the rate of one a week, undermining oil companies' claims to be doing everything possible to improve the safety of rigs.
Shell has emerged as one of the top offenders despite promising to clean up its act five years ago after a large accident in which two oil workers died.
Documents obtained by the Guardian record leaks voluntarily declared by the oil companies to the safety regulator, the Health and Safety Executive(HSE), in a database set up after the Piper Alpha disaster of 6 July 1988 which killed 167 workers. They reveal for the first time the names of companies that have caused more than 100 potentially lethal and largely unpublicised oil and gas spills in the North Sea in 2009 and 2010.
They also deal a significant blow to the government's credibility in supporting the oil industry's fervent desire to drill in the Arctic. Charles Hendry, the energy minister, has said operations to drill in deep Arctic waters by companies such as Cairn Energy off Greenland are "entirely legitimate" as long as they adhere to Britain's "robust" safety regulation.