Unexploded wartime bombs litter the seabed off the Dorset coast, which could host an offshore windfarm.

This was a surprise finding of a survey into the 280 sq km of sea, said Chris Sherrington, project director of Eneco, which aims to build a £3 billion offshore windfarm from Purbeck to the Needles on the Isle of Wight.

“There’s quite a lot out there,” he told Poole Harbour Commissioners annual open evening. A specialist survey undertaken during the summer had revealed large numbers of unexploded ordnance on the seabed.

The wind project would have between 180 and 300 wind turbines, depending on their size and the nearest part of the zone to the coast would be eight miles away, he said.

Turbines would be in 30-50 metres of water and he said the survey aimed to ensure there was no ordnance where they intended to drill.

“There is quite a lot of potential ordnance from World War I and World War II out there,” he said.

Mines and wartime bombs are occasionally pulled up with the catch in fishermen’s nets and have to be safely exploded by service bomb disposal units.

Robert Key, former MP for Salisbury who retired at the April general election, narrowly escaped being blown up by a wartime mine on Swanage beach in 1955, which killed five children.

As an MP he discovered that 58 out of 117 mines laid were still unaccounted for, despite the beach being cleared three times and it was thought the mine that exploded had been washed ashore in a gale.

Mr Sherrington said they hoped to go to the planning authorities for the windfarm at the end of 2012 and if successful construction could start in 2014.