The long-term effects of the BP oil spill in the Gulf of Mexico are likely to be small, a group of leading scientists said yesterday, but some of the clean-up methods may be doing more harm than good. Their views contradicted those of the White House, which has described the oil spill as the "worst environmental catastrophe" to hit the US, and has ordered BP to make greater efforts to clean up the spill...Simon Boxall of the UK's National Oceanography Centre at Southampton University said that the experience of previous oil spills - including the Exxon Valdez and Torrey Canyon disasters - showed that in some cases "the clean-up caused far more damage than the oil itself". Burning off the oil, for instance, as BP has been doing, caused other forms of pollution and was ineffective, he said.