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* Some scientists dismayed by "gung ho" attitude to cleanup
* Doing nothing might have been better for environment
* High political stakes weigh against laissez faire approach
By Kate Kelland, Health and Science Correspondent
LONDON, June 28 (Reuters) - It might have been better for the environment to have done nothing about the enormous oil spill in the Gulf of Mexico except to keep the oil out at sea, British scientists said on Monday.
Marine biology and environmental experts said they feared the aggressive cleanup operation, during which oil has been set alight and oil-dispersing chemicals have been dumped into the sea, might be more damaging than the oil itself.
Previous experience suggests that containing the oil out at sea but otherwise leaving it alone to disperse and evaporate naturally is better in the long run but is regarded as politically unacceptable, they said.
"One of the problems with this spill is that it has gone from the environmental arena into the economic and political arena, so if you ask how bad it is, that depends on which perspective you're coming from," said Martin Preston, an expert in marine pollution, earth and ocean sciences from Britain's Liverpool University.
"Economically, clearly the impact has been very large, but environmentally the jury is still out. One of the tensions between environment and politics is that politicians cannot be seen to be doing nothing, even though doing nothing is sometimes the best option."
Scientists told the briefing in London that although the Deepwater Horizon rig blowout and explosion, the death of 11 workers and the leak added up to a major incident, they did not yet constitute an environmental catastrophe.
The U.S. government estimates that up to 60,000 barrels (2.5 million gallons/9.5 million litres) of oil a day are spewing from the damaged BP Plc oil well on the seabed about a mile (1.6 km) below the surface.
Much of the oil is still far out at sea, but some is starting to drift towards the southern U.S. coast, where Louisiana's fragile wetlands have been hardest hit so far.
BP and the Obama administration have been under pressure from the public to take serious action to clean up the oil.
Opinion polls have shown that the U.S. public disapproved of BP's response to the spill and grew more sceptical about the Obama administration's response in the weeks after the accident.
The spreading oil has halted major fisheries and covered wetlands and beaches from Louisiana to Florida. The public has been horrified by images of birds and other wildlife soaked in oil.
There have been around 20 major spills of more than 20 million gallons since the 1960s. The largest recent spill was in 1991 in the Gulf as a result of the Gulf War when between 240 and 460 million gallons were spilled.
The largest previous spill resulting from a rig blowout like that of the Deepwater Horizon was the Ixtoc 1 off Mexico's Gulf coast in June 1979, which continued for 9 months during which more than 140 million gallons of oil was spilled.
The Exxon Valdez accident in Alaska in 1989 spilled around 10 million gallons.
Simon Boxall, an expert at Britain's National Oceanography Centre who has helped analyse various major oil spill cleanups, said several detailed experiments had been conducted since the Exxon Valdez spill, looking at areas that were left alone, as well as at areas cleaned up chemically or mechanically.
"The chemically cleaned up areas have taken the longest to recover and they are still damaged," Boxall said. "The areas that were left alone actually recovered much quicker."
Some 10,000 people were flown in to deal with the Exxon Valdez spill, and Boxall said scientists now wondered whether the "cleanup town" that grew up around it caused more environmental damage than the oil itself.
Christoph Gertler of Bangor University, who has been studying various potential bacterial remedies for oil spills, said reports by the U.S. National Oceanic and Atmospheric Administration suggested that dispersants were "changing the nature of the oil in a very unfavourable way", making it more difficult for naturally occurring marine bacteria to break it down.
Boxall said it was important to remember that oil coming from the BP well was a light crude that would break down and evaporate fairly quickly when it came to the surface.
He said there were three golden rules of oil spills:
"The first is don't spill it in the first place: the second is, if you do spill it, try and pick it up as quickly and easily as possible," he said. "And the third is that in the open ocean, the best thing to do is leave well alone. Unfortunately, politically that always looks like a cop-out."
Scientists agreed that the wetlands of Louisiana were the most sensitive areas at risk, but said that here again a light touch might be the safest solution.
"The more delicate an area is -- and many of these areas around the Gulf coast are very delicate -- the more significant is the risk of making things worse by acting," said Preston. "A rather gung-ho attitude to the cleanup could end up doing more damage than if it had simply been left alone." (Editing by Maggie Fox and Tim Pearce)