Britain's largest gas supplier, Centrica, received the go-ahead from the competition watchdog on Monday to start using more capacity at its huge subsea Rough gas storage facility in the North Sea.

The utility can with immediate effect use up to 25 percent of its own capacity at Britain's largest gas storage facility, up from 15 percent previously allowed.

The gas supplier submitted a request in April 2010 to the Office of Fair Trading (OFT) to suspend operational restrictions at Rough on the grounds that market conditions had changed since it purchased the site in 2003.

Centrica argued that more sources of flexible gas, notably liquefied natural gas (LNG), had become available to the market and that the introduction of the EU's Third Internal Energy Market Package - new rules focused on increasing competition - would replace many of the laws set out for Rough.

The request was then passed on to the Competition Commission, which rubber stamped rule changes on Monday.

Rough can cover around 10 percent of Britain's peak-day gas demand and is located in the North Sea around 30 km off the east coast of Yorkshire.

(Reporting by Karolin Schaps; editing by James Jukwey)