An influential conservation group founded in the 19th century to safeguard Hampstead Heath has surpassed 2,000 members for the first time in its 118-year history.

The Heath and Hampstead Society, which also exists to preserve Hampstead Village, credited its battle with the City of London Corporation over the future of the Heath for sparking the “huge rise” in support.

The society has been leading the Dam Nonsense campaign against the City’s £15million ponds project.

Chairman Marc Hutchinson said: “We are delighted and immensely encouraged by this unprecedented level of support from people who feel strongly that Hampstead Heath and Hampstead must be preserved and protected.

“A major factor in this huge rise in our membership is the public’s backing for the legal proceedings which the society has now launched against the City of London to challenge the legality of the ponds project, a reservoir-related engineering project which will severely disfigure important parts of the historic Heath landscape.”

The society has issued legal proceedings at the High Court, as it seeks a judicial review to overturn the City’s decision to press ahead with the project.

Both sides will be applying to the court for an expedited hearing, which could take place as soon as next month.

Mr Hutchinson added that the society’s boosted membership has helped it to raise £90,000 to fund the legal proceedings, towards a target of £100,000, which “clearly shows the strength of the overwhelming public disapproval of the ponds project”.

Under the controversial scheme, the City wants to enlarge dams across the Heath to ensure they never collapse, even in the most extreme storm that is theoretically possible.