Questions have also been raised over its planned investment in the London Array, which would be the world's largest offshore wind farm, where costs have risen sharply and Royal Dutch Shell, one of the three partners, has decided to pull out.
Wind Farms
Supplier warns of higher energy prices
Shell chief says all energy sources must be tapped
In February, its parent company, Royal Dutch Shell, said it would maintain a broad portfolio of renewable resources including biofuels, hydrogen, solar, wind and nuclear power. That came after company chief executive officer Jeroen van der Veer said in January that supplies of easy-to-access oil and natural gas would fail to meet global demand for such after 2015.