"Around the world there's evidence that creating marine reserves -- areas where fishing is not allowed -- leads to a several fold increase in the size and number of fish, shellfish and other animals," commission chairman Tom Blundell said.

"A third of the Great Barrier Reef is closed to fishing and countries like New Zealand and South Africa have plans to designate between 10 and 20 percent of their marine environment as reserves," he added.

But they were the exception, leaving only a minuscule fraction of the world's oceans protected from the depredations of commercial fishing.

The commission said the move was affordable, citing figures that suggested closing 30 percent of the world's oceans would cost up to 7.5 billion pounds ($14.5 billion) a year compared to the 16 billion pounds spent subsidising commercial fishing.

The commission, an independent body providing non-binding advice on environmental issues to the UK government, has spent the past 18 months studying the issue.

It urged Britain to lead the way by declaring 30 percent of its coastal waters no-go areas for fishing, and hoped the 25-nation European Union would follow suit.

"We are suggesting that the 30 percent protected areas should be spread globally. There is a growing number of international bodies moving in this direction," economist and commission member Paul Ekins told a news conference.

Environmental pressure group Greenpeace welcomed the call but fisheries organisations said it was unnecessary as limited conservation measures around Britain had already produced a rapid recovery in stocks.

The commission, though, said single-species conservation programmes were no longer enough.

"We are facing probably the greatest challenge after climate change," said scientist Ian Graham-Bryce.

What was needed was a comprehensive, ecosystem approach that extended to the world's seas the kind of protection given to nature reserves and wildlife parks on land.

"Less than 0.5 percent of the world's oceans are protected compared with 12 percent of land," Graham-Bryce added.

The commission -- which four years ago was laughed at for calling for a 60 percent cut in carbon dioxide emissions, a figure that is now a British government target -- reserved its most scathing criticism for deep sea bottom trawling.