A Carleton Rode fishery owner is suing his neighbours for £5.5m, after claiming work to dig four lakes nearby caused losses to his fish stocks and harmed his business.

Bryn and Joanna Chetwynd run Fen Lakes Fishery, a designated County Wildlife Site and area of fenland along the banks of the River Tas.

But the couple claim their ponds have been affected by works carried out by neighbours Barry and Caroline Tunmore to create four lakes - and have asked the High Court to order them to fill in three.

They are seeking £5.5m to restock their ponds with fish and cover losses in their income.

Opening the case last week, Wayne Beglan, for the Chetwynds, said: 'Throughout the history of this matter, the claimants have taken a very clear and consistent line that the primary cause of their difficulties were the defendants' excavations.'

The court heard how the lakes - which cover a total area of more than 8,000 square metres - were built without planning permission between 1999 and 2006 on land surrounding their home, which neighbours Fen Lakes Fishery.

South Norfolk Council granted the Tunmores retrospective permission in 2008 - but this was quashed by the High Court two years later, after Mr Chetwynd brought a successful judicial review challenge.

The Chetwynds claim excavation works lowered the water table by disrupting the supply of water to the ponds of their lake and claim their losses include £75,000 worth of fish stocks.

But the Tunmores say there was 'no significant flow' from their lakes to the Chetwynds' ponds, and say that it was 'woeful' management of the fishery on Mr Chetwynd's behalf that 'materially contributed' to the loss of his fish.

Wayne Clark, representing the Tunmores, said: 'At the end of the day, the defendants will contend the evidence will show that the claimants' poor management practices contributed in a material manner to the fish losses alleged.'

He said while one lake may have had a 'limited impact' on one of the ponds, there was 'insufficient' evidence to prove this caused the loss.

The hearing continues and the judge is expected to reserve his decision until after the New Year.