London Array will not go ahead with the second phase of an offshore wind farm, partly because of the time it would take to assess the impact on birds, it has been announced.
The consortium behind the Thames Estuary development said there were "technical challenges and environmental uncertainties" surrounding the site.
There would be a wait of at least three years to assess the potential impact of additional turbines on the habitat of red-throated divers.
London Array said it had formally requested the Crown Estate to terminate the agreement for lease of phase two and has cancelled the remaining grid capacity it had reserved at a National Grid substation in Graveney, Kent.
General manager Mike O'Hare said: "Phase two has always been subject to a Grampian condition requiring London Array to demonstrate that any change caused by the additional turbines to the habitat of the red-throated divers that over-winter in this part of the Thames Estuary would not compromise its status as a designated environmental special protection area.
"We believe it will take until at least January 2017 for that data to be collected and although initial findings from the existing phase one site look positive, there is no guarantee at the end of three years that we will be able to satisfy the authorities that any impact on the birds would be acceptable.
"In the absence of any certainty that phase two would be able to go ahead, our shareholders have decided to surrender the Crown Estate agreement for lease on the site, terminate the grid connection option, and concentrate on other development projects in their individual portfolios. Our existing operations at Ramsgate and staffing levels are unaffected."
London Array's wind farm is already the biggest of its kind in the world.