Developed by Dong Energy, E.ON and Masdar, London Array is located off England in the outer Thames Estuary, 20km from the coasts of Kent and Essex.
Powered by 175 turbines Siemens turbines, the wind farm has a capacity of 630 MW – enough to power nearly half a million homes.
Mr Cameron said the opening of London Array was “a great day for Britain and a big win for renewable energy”.
“London Array shows you can build large scale renewable energy projects right here in Britain,” he said. “This is because when it comes to clean energy, the UK has one of the clearest investment climates globally”.
Maria McCaffery, chief executive of trade group RenewableUK, said Mr Cameron’s "ringing endorsement of Britain’s offshore wind industry is a real boost for the entire renewable energy sector, which is a key growth area for the British economy”.
She said London Array was “a magnificent feat of green engineering in a field in which Britain is the global leader, as we have more offshore wind capacity installed than the rest of the world put together”.
And she added that the Prime Minister had assured her that the government would back the UK wind industry. “Such a strong signal from the very top of our political establishment will help to put an end to the siren calls from the naysayers who’ve failed to appreciate the scale of the opportunity Britain has here. We need to maintain our pole position in offshore wind energy to reap the full economic and environmental benefits.”
London Array is 50 per cent owned by Danish energy company Dong, with Germany’s E.ON holding 30 per cent and Masdar from Abu Dhabi holding the final 20 per cent.