Campaigners have vowed to block plans to build a giant tomb on a patch of greenbelt land near a rural village road.
Proposals to build the first multi-faith mausoleum in England next to the Westminster Cemetery, in Milespit Hill, were submitted to Barnet Borough Council last month.
But neighbours say the new building – in which hundreds of people would be interred - will be “astronomical” in size, “wreak havoc” on wildlife in the area and cause traffic chaos.
The land has already been classed for use as a cemetery - even though it was last used as a pig farm before the Second World War and has never housed any graves.
Labour GLA member for Barnet Andrew Dismore, who is leading the campaign against the development, said: “It’s deeply worrying. It goes way beyond what should be permitted and it is masquerading as a cemetery.”
The issue has now become a cross-party matter of concern and opponents are also being backed by Conservative MP Matthew Offord.
Barnet Council leader Richard Cornelius has also described the application as “totally inappropriate for Mill Hill”.
The land was once owned by Westminster Council, but was sold off for just five pence in the 1980s.
Developer Monument Properties Investment is now looking to build on the Grade II listed conservation area.
But the Westminster Association of Relatives (WAR) – made up of next of kin of the deceased in the neighbouring cemetery – is fighting the plans.
Chair of WAR, Eileen Sheppard, of Arkley Park, said: “I grew up here and remember it being a beautiful place - but this will just ruin everything we have all loved about this area.
“It is too big - I’d say it’s astronomical. It will be a dreadful thing for Mill Hill.”
The planning application features a columbaria - a storage room for urns - a new access road, and a 43 space car park, which would involve destroying trees which opponents claim have preservation orders.
Richard Logue, chair of the Mill Hill Residents Association, said: “It’s not a mausoleum, it’s a necropolis.
"There’s going to be a huge demand for it so in an area where traffic is already heavy, they should be finding ways to keep it down.”
Campaigners also argue the development will ruin the habitat for wildlife in the area, which is believed to include badgers, hedgehogs, sloe worms and deer.
Peter Smallwood, of Monument Properties Investment, said he and his co-owners were more than happy to listen to the objections of neighbours.
He said: “We will listen to what they have to say – we won’t just ignore them. We want to speak with them and hear what their concerns are.
“There is a chronic shortage of burial space in this country and mausoleums are becoming more accepted. We feel it is an appropriate place to put one and it is a sensible use of the land.”