LONDON | (Reuters) - Britain's worst oil spill for over a decade appeared to be entering its final stages, as the leak from Royal Dutch Shell's faulty North Sea pipeline slowed to a trickle.
"The flow line leak is reduced to less than two barrels per day," Glen Cayley, technical director of Shell's European exploration and production activities, told BBC Radio 4 on Tuesday.
Environmental groups criticized the company for a lack of transparency and the delay before news of the spill was made public.
Further detail emerged on Tuesday as Shell said oil seepage was continuing from a different part of the same faulty pipeline, dismissing reports of a second leak.
"The leak source remains the same. The initial release path was stopped on Thursday; however, the oil found a second pathway to the sea. There is no new leak," Shell said in a statement.
A Scottish government spokesman said the impact of the spill on fishing had been reduced as the size of the spill had shrunk, and fishing continued as normal away from the affected area.
Sensitivities remain high about marine oil leaks and the availability of accurate information concerning their scale in the aftermath of BP's massive Gulf of Mexico spill last year.
Reuters revealed on Saturday that the spill on Shell's Gannet field, which it co-owns with Exxon Mobil Corp and which lies 180 km off the Scottish port of Aberdeen, had been leaking for two days before authorities or Shell revealed it.
Speaking in the radio interview, Cayley defended the company's initial silence, saying the leak was located among complicated underwater infrastructure.
"Only when we had confident information, really, did we want to share that, and since Friday we have issued daily bulletins and updates," he said.
The government said Shell informed it of the oil leak on Wednesday, and its first focus was on ensuring Shell complied with its oil pollution emergency plan and took action to minimize the environmental impact before it publicized the spill.
"When that work had been started and the extent of the leak became clear, Shell informed the public," Britain's Department of Energy and Climate Change said in an emailed statement.
The company was not able to give an estimate of when it expects the pipeline to stop seeping oil, a spokesman said.
Shell said around 216 tons of oil, equivalent to 1,300 barrels, had leaked into the North Sea in a "significant spill," but the rate at which it was flowing had been reducing since Wednesday, when a well was shut off.
Shell shares were down 1.3 percent to 1990 pence at 1030 GMT, marginally underperforming the European index of oil and gas companies, which was down 1.1 percent.
"There are these types of leaks all the time, especially in mature basins with mature infrastructure. It will keep happening, but the industry is very well equipped. You have seen in the last few days they've got it down to two barrels," said Sanford Bernstein analyst Oswald Clint.
Cayley said Shell was confident that oil from the leaking pipe would not reach shore.
"At its maximum the sheen on the surface was some 30 kilometers in length, but thanks to fairly harsh weather conditions that has now diminished," he said, noting waves had helped to disperse the slick.
Greenpeace spokesman Ben Ayliffe, echoing concerns expressed by the Royal Society for the Protection of Birds on Monday, said: "Any oil spill has the potential to significantly impact things like the birds, especially when we are this close to the breeding season."
Editing by David Holmes and Will Waterman