A much-loved pond on a village green has been drained in a £20,000 project to rid it of illegal fish.

Prussian carp, an invasive species from East Asia and Central Europe, were found in the water at Matfield, near Paddock Wood.

They are considered a risk to native fish and importing them or releasing them in the wild in England is banned.

An enforcement notice to remove them was issued by the Environment Agency.

The green, the largest in Kent, is maintained by Brenchley and Matfield Parish Council.

A letter from the government agency to the parish council said: “They can hybridise with other carp... and the females can produce clones of themselves by utilising the sperm of other fish to activate egg development.

“This and the wide range of habitat and food they can use can lead them to dominate waters they are introduced to.

“Due to the risk they pose to native fish and fisheries it is illegal to either import live Prussian carp into England or to release them into the wild in England.”

For this reason, the agency told the parish council it needed to “eradicate” the fish from the pond.

Work started this month, which included draining the water, removing the rogue fish – of which there were thought to be several ton – covering the bottom with hydrated lime and leaving it for two weeks.

In a statement, the parish council said: “No one locally wants this to happen but sadly it is unavoidable.

“Once this phase is over, everyone can look forward to a brighter more sustainable future for the pond we all love so much.”

A spokesman for the parish council said it was not clear how the carp ended up in the pond but it was possible someone thought they were doing a good deed by releasing them but it had actually turned into a “disaster”.

The project, costing around £20,000 in total, is now in its second phase which includes digging deeper pockets of water, removing vegetation, working on the islands, repairing the retaining wall, creating areas for wildlife, adding land drains and replanting wildflower seeds and lilies.

This is expected to take another two weeks to complete and then the pond will be left to refill with rainwater.

The parish spokesman said it was taking the opportunity to do the extra work now as it had not been touched for a few years. In future, there would be an annual maintenance schedule, they added.

A decision on whether any fish can return to the pond has not yet been made.

The parish council has around £132,000 in precepts this year meaning the pond project is costing around 15% of this but it is not being funded by it, instead the council reserves are being used.

An Environment Agency spokesman added: “Our local specialist fisheries officers have given advice to Matfield Parish Council on long-term improvements it can make to the village pond, which it owns and operates, after a number of water quality issues.

“We have since removed suspected invasive species for tests as part of our work to protect fish, ecosystems and other wildlife from the damage they pose.”

In May, the agency issued a national warning over the threat Prussian carp posed and urged people to report any suspected sightings.

The species has been introduced in many countries, either on purpose or not, due to their similarities with other types of carp and brown goldfish.

Identifying them can be extremely difficult but a number of features can be used to distinguish them.

They are deep-bodied, around 35cm in length with large scales, and are often silvery in colour, but larger specimens can be a golden brown and they lack barbules – a whisker-like organ near their mouth.

Anyone who has concerns about water quality in ponds, lakes and rivers or sees dead fish or others in distress can call the Environment Agency incident hotline on 0800 807060.