A High Court decision against a campaign to save Hampstead Heath from being “permanently disfigured” by a £15million ponds redevelopment project will not be appealed against, the main campaign group has said.

The Heath and Hampstead Society, which had launched a £100,000 fundraising campaign to fight the City of London Corporation, has abandoned its legal fight after being advised by their solicitors that an appeal is “unlikely to succeed”.

It comes shortly after the influential civic group, which was originally founded to protect the wild and natural state of the Heath, was dealt a major blow after losing its High Court battle to block the City’s proposals to enlarge dams and build new ones.

The City, which managed the Heath, says the works are needed due to the deadly threat the collapse of the dams would pose to downstream communities.

Campaigners running the Dam Nonsense campaign, led by the Heath and Hampstead Society, said the plans would “permanently disfigure” the Heath and that the risk of collapse each year was an astronomical 1-in-400,000.

While choosing to give up its fight through the courts, the Society says it intends to continue its battle against the project by opposing the planning application for the project and make formal representations to Camden Council.

A statement released by the Heath and Hampstead society read: “The Trustees have been advised, both by their counsel and their solicitors, that an appeal is unlikely to succeed, even though, as the trial judge found, we had an arguable case, and even though we still feel that the merits of the case are on our side.

“However the law appears to be against us, something at which we remain deeply dismayed.

“Accordingly, and with great reluctance, the Trustees have decided not to seek leave to appeal from the Court of Appeal.

“The costs of seeking leave would require the Society to raise significant further funds from its members and others and they do not feel entitled, in all the circumstances, to ask those, who contributed so promptly and generously to the £100,000 fundraising appeal for the initial proceedings, to contribute further funds when the prospects of success are not favourable.”

The City plans to begin work early next year. The scheme is expected to take about two years and will see significant engineering works across the Heath.

Visitors will be faced with construction and pond closures throughout much of that time.

The council is expected to consider the planning application in the New Year.

Bob Warnock, the City Corporation’s Superintendent at Hampstead Heath, said: “The judge’s decision shows that our interpretation of the law and guidance is correct – and it means that the Heath’s landscape can remain at the heart of the scheme.

“We are protecting the Heath, improving its habitat, ecology and water quality, whilst ensuring that the earth dams are strong enough to meet modern safety standards.

“We have a legal duty to make sure the dams on the Heath do not fail, an event which would have serious consequences to the residential community downstream.

“We have a good relationship with the Heath & Hampstead Society and we will continue to work with them on the Ponds Project and Heath management issues across the board.”