Community groups are calling on the council to listen to their concerns and their own officers’ recommendations and dismiss plans to demolish and rebuild a Highgate mansion overlooking Hampstead Heath.

Developers hoped to replace the existing four-bedroom mansion in Highgate with one more than twice its size, but opponents claim the lengthy construction process would damage the conservation area and risk flooding the Heath.

Following an extraordinarily long consultation period of four and a half years, planning officers are recommending the plans for thrown out when they go before Camden Council next week.

The Friends of Millfield Lane have campaigned hard to prevent the development, known as The Watergate, which they claim will ruin the character of their leafy road, which connects Parliament Hill to Kenwood.

Karen Beare, on behalf of Friends of Millfield Lane, said she fears if the plans were given the green light, the lane would eventually have to be rebuilt from scratch.

She said: “By essentially prioritising construction traffic for more than two years, this development would cause considerable and unacceptable loss of enjoyment for those who take pleasure from ambling along this tranquil lane.

“The ground compression caused by so many heavy lorries passing along the lane over such a long period will crush all the tree roots below ground, because it can’t cope with the weight.”

A petition against the development gathered more than 4,000 signatures, and campaigners also produced a video to show the impact of allowing HGVs to begin rumbling through the narrow lane.

They claim even smaller HGVs could only access the site by removing the historic railings to the Ladies’ Pond and chopping down three “substantial” trees.

Jane Shallice, Chair of Kenwood Ladies Pond Association, said: “It’s no wonder that the developer hasn’t even had the courtesy to contact us to discuss his plans.

“The Ladies’ Pond is known as a sanctuary. The women who swim at the pond have been both angered and devastated by these proposals, but are encouraged that after so many years of campaigning Camden have apparently come to their senses and now consider them unacceptable.”

There are further concerns over the developer’s proposed drainage scheme around a planned basement, which opponents say is unlawful and would risk flooding the Heath and a neighbouring property.

Sally Gimson, Labour councillor for Highgate, said: “I am pleased to see that Camden Council planning officers have recommended refusal for this ill-conceived scheme, and I fully support many of the objections raised by concerned members of the public – both local residents and the many users of the Heath affected.”

Her comments were echoed by fellow Highgate councillor and Green Party mayoral candidate, Sian Berry, who said: “This misconceived scheme has threatened the local residents and users of the Heath with untold noise and disturbance for several years, and must now be refused. I hope the councillors on the committee will take note of the huge opposition and the solid practical reasons for refusing the scheme and stop this.”

The planning committee will make its final decision next Thursday.