Shell said projects in the US offered more competitive returns
A company based in Abu Dhabi has bought a 20% stake in London Array offshore wind farm, which is set to be one of the largest in the world.
The planned 1,000 MW project in the Thames Estuary off the Kent and Essex coasts could power three quarters of a million homes.
Masdar and energy firm E.ON announced the joint venture on Thursday.
Representatives from both firms were meeting government ministers at Downing Street to discuss the project.
E.ON said it was hoped the first stage would be completed in 2012 and would consist of up to 175 turbines.
It said the wind farm would eventually have up to 271 turbines.
A statement from both companies said the firms planned to work together on a range of renewable energy projects.
Before the deal was made, E.ON owned half of the wind farm project and DONG Energy owned the other half.
Masdar bought 40% of E.ON's share, giving it a 20% stake in the whole enterprise.
E.ON chief executive Dr Wulf Bernotat said the project would raise "important challenges".
"The lessons we learn will be vital for the development of the next generation of offshore projects.
"We have secured in Masdar a strong partner to work with us on the London Array scheme and on future renewable energy projects which will help push the industry to its next stage," he said.
Chief executive of Masdar, Dr Sultan Al Jaber, said: "London Array is an important investment for Masdar into the wind sector.
"We believe that the offshore wind market will be a major force in the future and this is a very opportune time for us to enter this developing segment of the renewable energy market."
He said Masdar hoped to build a partnership with the UK Government "to drive the future growth of the renewable energy sector for the benefit of both our economies".