The UK currently generates more than six gigawatts (GW) of electricity from wind power. The target for 2020 is 33GW, about 15 per cent of total electricity, of which 18GW will come from offshore.
The first offshore wind farm in the UK, based near Blyth off the coast of Northumberland, went fully operational in December 2000 with just two turbines, compared to the 568 offshore turbines the UK has now.
Siemens employs more than 8,000 people in the turbine business alone.
It is forecast that the installation of offshore wind farms up to 2022 will add around £60bn to the UK economy.
It will raise around £14bn for the Treasury and support over 45,000 long-term jobs.