Caygill likened the rescue to an incident last month when a pilot landed a damaged US Airways plane on the Hudson River in New York, saving all 155 people on board.

"I suspect the pilot of this helicopter played a very major part in ensuring all the passengers and crew were alive when they were rescued," he said.

"It would have been very difficult for the passengers not least because you're in an aircraft, you've gone into the water, you're in the dark and you have to get yourself to a life raft."

Caygill said it was too early to say what had caused the incident and that it was unclear whether the helicopter had been landing on or taking off from the platform.

The flight was one of the thousands a year that service the many oil and gas platforms in the North Sea.