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. The documents...record leaks classed by the regulator as "major" or "significant", which, if ignited, could cause many deaths…A Shell spokesman said: "No spill is acceptable and we have made progress. We work closely with regulators and invested over a billion dollars in recent years to upgrade facilities across the North Sea to continue this improvement of our performance."...Whistleblowers [claim]...accidents are kept quiet...because workers fear they cannot report them in case they lose their jobs...Robert Paterson, health and safety director of the Oil & Gas UK, which represents the industry...said oil companies last year agreed to "redouble efforts to reduce the number of leaks by 50% over three years and many companies are building this target into their business plans". He rejected the whistleblowers' concerns [also refers to Cairn Energy, Maersk, Talisman, BP]