A huge expansion of the London Array wind farm off the north Kent coast will not go ahead, it has been revealed today.

A statement from the consortium behind the world's largest wind farm put the decision to halt the next stage of development down to various factors - including uncertainty over the potential impact on birds.

They included a review by consortium members of their portfolios, the technical challenges and environmental uncertainties surrounding the site. The latter demands a wait of at least three years until Phase 2's potential impact on birds could be completely assessed.

General manager Mike O'Hare said: "Phase 2 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 overwinter 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 1 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."

Red throated divers are a migratory bird on the RSPB's amber list for bird species at risk. They are mainly concentrated in Shetland and around the north coast of Scotland and its islands. Outside the breeding season they are numerous along the UK's east coast.

Mr O'Hare added: "In the absence of any certainty that Phase 2 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 has formally requested The Crown Estate terminate the agreement for lease for the Phase 2 area and has cancelled the remaining grid capacity it had reserved at the National Grid substation at Cleve Hill in Graveney.

The original consent for London Array was for a wind farm of up to 1000MW, with 630MW in Phase 1 – which is complete, fully operational and the world’s largest offshore wind farm with.

It was formally inaugurated by Prime Minster David Cameron at a high-profile event in Margate last July.

Mr Cameron then described London Array as a "huge win" for Kent, renewable energy and Britain.

Phase 2 had the potential to provide capacity for a further 370MW although known constraints on site resulted in plans for just 240MW being drawn up with an expectation that the final capacity would be closer to 200MW.

Mike O'Hare added: "The Phase 2 site is technically more challenging than Phase 1 with a large area in very shallow water. Additional issues include a difficult and longer route for the export cables and an exclusion zone for aggregates operations.

"Phase 1 is performing very well with January 2014 London Array’s second successive record month for the amount of electricity generated. Our shareholders remain committed to offshore wind in the UK, however the combination of environmental uncertainties, technical challenges and the option to develop other sites has resulted in their decision not to proceed with Phase 2."

The project consortium is made up of DONG Energy, who own 50%, E.ON (30%) and Masdar (20%).

Construction on London Array began in 2009. Phase 1 is a distinctive feature lying north east of Thanet, covering an offshore area of more than 62sq miles.

The highest point of each turbine blade is 147 metres, taller than the London Eye. The lowest point is 22 metres above the sea.

More than 75 organisations helped build London Array, involving 6,700 people, half of them British. The project also involved 120 Kent companies

Phase 1 includes two offshore substations, 280 miles of offshore cabling and one onshore substation

It produces 630MW of electricity, enough to power nearly half a million UK homes each year – two thirds of the homes in Kent.

The wind power created represents carbon dioxide savings of 925,000 tonnes a year.