Construction of the 900 megawatt (MW) windfarm is expected to begin in 2017 and it will be able to produce enough electricity to power 800,000 homes a year, the joint statement said.

Financial details of the deal were not revealed.

"Securing partners for projects such as Triton Knoll has been a key objective in our renewables strategy," Hans Buntin, CEO of RWE's renewable energy subsidiary Innogy, said.

RWE's renewable energy subsidiary Innogy last year scaled back capacity of the project, located off England's east coast, to make it more economic.

Britain is the world's biggest offshore wind market and aims to defend its lead by multiplying current capacity to around 10 gigawatts (GW) by the end of the decade.

"This is another vote of confidence in the world's number one offshore wind market which is continuing to attract investors from all over the world," British energy and climate change secretary Ed Davey said in the statement.

Offshore wind farms are some of the most expensive renewable energy projects because they are built far out at sea.

Separately, Britain's energy market regulator Ofgem on Thursday granted a licence to the Balfour Beatty Equitix consortium to own and operate a 352 million pound transmissions cable to RWE Innogy's Gwynt y Mor 576-megawatt wind farm, off the coast of North Wales.

The cable will allow the project, which was completed at the end of last year, to connect to Britain's onshore electricity grid.

(Reporting by Susanna Twidale Additional reporting by Nina Chestney; Editing by Mark Potter)