Contractors laying massive electricity cables through the Norfolk countryside have been issued with a warning from the Environment Agency after they polluted a chalk river.

Officials have written to VolkerFitzpatrick - which is carrying out the work to bring power onshore from North Sea wind farms - following a series of incidents which saw silt pour into the River Glaven.

Conservationists say the waterway will take years to recover from the impact of the pollution, which took place during periods of heavy rainfall last autumn.

A view of the Hornsea Three trench being dug, showing Kelling Heath, the village of Weybourne beyond it, and the north Norfolk coastA view of the Hornsea Three trench being dug, showing Kelling Heath, the village of Weybourne beyond it, and the north Norfolk coast (Image: Mike Page)

Since then, Environmental Agency officials have carried out a number of visits to the cable-laying works and last month wrote to the company in a bid to ensure there is no repeat of the incidents this year.

The company is digging a 33 mile, 262ft wide trench from Weybourne, on the coast, to Swardeston, south of Norwich, on behalf of Orsted - which calls itself the "world's most sustainable energy company".

Last year, material dug up from the trench flowed into the Glaven, which runs for 10 miles from Selbrigg Pond, near Holt, out into the sea at Blakeney Point.

READ MORE: Orsted Horsea Three wind farm blamed for River Glaven pollution

A spokesman for the EA said: "The Environment Agency issued a warning letter to VolkerFitzpatrick for allowing silt to enter the River Glaven following episodes of heavy rain in September, October and November the previous year.

"Environment officers have visited the site 15 times over the last year and have been working with the company to ensure robust plans and procedures are in place to manage the risk of any further pollution of the river resulting from the works.

"The Glaven is a precious chalk river which must be protected from pollution events and silt ingress."