Campaigners against plans to rebuild a Highgate house on the edge of Hampstead Heath as a contemporary home with two basements have said time is running out to object to the proposals.

They fear construction works would transform a quiet woodland track leading up to Kenwood into a busy access route for lorries driving up and down from the building site.

The owners of the Water House want to demolish and rebuild the 1990s home as a two-storey modern house with floor-to-ceiling glass windows and two separate basements on the lower ground floor.

The plans have already attracted a large number of objections on Camden Council’s website, but Fitzroy Park resident and Water House neighbour Karen Beare is urging others to voice their views before the consultation period ends next Thursday.

“There are a number of issues and reasons to refuse the application,” she said. “All the local groups have come together as the Friends of Millfield Lane with a website to resist this development.”

If the revised scheme, an expansion of existing development proposals, is granted planning permission, a cinema and indoor pool will be created in the two basements, which are not connected.

SHH Architects disputes there are two basements, saying that just one basement will be created because the building sits on an existing slope.

But campaigners are worried that Millfield Lane will be turned from a quiet passage leading up to the Kenwood Ladies’ Bathing Pond into a dangerous route dominated by HGVs.

Mrs Beare added: “There is a problem with access, you don’t have to be a rocket scientist to know that. To widen the path, they will cut the trees and verges which will permanently harm the character.

A spokesman for SHH Architects said: “We’ve come up with a construction method which avoids vehicles during peak periods and limits the number of vehicles each day to four – four journeys in and four journeys out, except for a six-week period when we’ll need six vehicles each day.”

Managing director Graham Harris added: “The reference to a ‘mansion’ on the Friends website is misleading as it implies we are proposing to build some sort of grotesque palatial pile on the fringe of the park, which we are not.

“Our proposal is a well-considered modernist piece of architecture which subtly responds to the site and its surrounding environ.”

Simon Lee, the Superintendant of Hampstead Heath, said the City of London Corporation, which runs the Heath, will be objecting to the proposals.