An energy giant behind two huge wind farms set to be built off the north Norfolk coast claims fewer birds will crash into the rotor blades if they are installed higher off the sea floor.

Swedish firm Vattenfall said taller turbines would make the sites safer for species including kittiwakes, gannets and black backed gulls.

But the RSPB said it was unconvinced the redesign - meaning blades would pass a minimum of 30 metres above the sea instead of 22 metres - would be enough to protect sea birds.

Eastern Daily Press: An illustration of Vattenfall's proposal to increase the height of its wind turbines by eight metres to provide more space for birds to fly around underneath.An illustration of Vattenfall's proposal to increase the height of its wind turbines by eight metres to provide more space for birds to fly around underneath. (Image: Vattenfall)

Kathy Wood, Vattenfall's head of consenting, said: "We are really happy that this engagement from communities and experts has led to sensitive design.”

But Andrew Dodd, RSPB's head of casework, said: “The RSPB welcomed the move by Vattenfall to increase the height of their turbines to try and reduce the impacts of their offshore windfarms on the UK’s globally important breeding seabirds.

"Unfortunately, the scale of threat posed by these proposed schemes is such that these changes will not be enough to prevent harm to our struggling seabirds, including kittiwakes which have been declining for decades."

Eastern Daily Press: A map showing the planned locations of Vattenfall's planned Vanguard (in yellow) and Boreas (in blue) wind farms. Cabling for the project would make landfall at Happsiburgh, and run across to a new substation at Necton, near Dereham.A map showing the planned locations of Vattenfall's planned Vanguard (in yellow) and Boreas (in blue) wind farms. Cabling for the project would make landfall at Happsiburgh, and run across to a new substation at Necton, near Dereham. (Image: Open Street Map data/Vattenfall)

Vattenfall's planned Vanguard and Boreas wind farms would have a total of 360 turbines and would be installed east of Norfolk, roughly parallel with the north Norfolk coast.

Cabling would make landfall at Happisburgh and run over to a new substation to be built next to an existing one in Necton, between Dereham and Swaffham.

Eastern Daily Press: Vattenfall is planning to build two large windfarms in the North Sea called Boreas and Vanguard.Vattenfall is planning to build two large windfarms in the North Sea called Boreas and Vanguard. (Image: Vattenfall)

Vanguard was approved in July last year, but a judicial review into the decision was later ordered by the High Court, which has not yet been resolved.

The Planning Inspectorate is due to rule on Boreas by April 12.

Mr Dodd said it was not only up to firms like Vattenfall to reduce the threats to nature posed by offshore wind.

He said: "These are a symptom of poor planning and must be urgently addressed by the UK government if they are to deliver on their ambitious targets for offshore wind. We are keen to work with industry and planners across the UK to find joint solutions for climate and nature.”

Mark Trinder, an ornithologist from the consultancy firm MacArthur Green, said: "Early on, site consultation and data gathering meant that the wind farm areas were chosen further offshore, as far away as possible from coastal bird breeding sites.

“All infrastructure projects have some form of impact, but Vattenfall has done everything possible to sensitively design the Norfolk projects.”