Monty Python star Terry Gilliam has accused a developer of sticking two fingers up to the public with plans to demolish a historic house on the edge of Hampstead Heath – and called on Camden Council to be “strong” in fighting the proposals.

Speaking to the Ham&High, the critically acclaimed film director and Highgate resident said the plans to knock down 19th century Athlone House and replace it with a luxury mansion – complete with a ballroom, basement swimming pool and roof terrace – were an “outrage”.

He urged the council not to be “weak” and to stand up to the owner and developers.

“Why Camden Council isn’t fighting this is beyond me,” he said.

“This whole battle is really down to the owners of Athlone House not honouring the commitment to restore the house. The council should be forced to enforce this agreement.

“It makes me mad because there really is nothing quite like the Heath in any other city in the world and the building they propose will look completely out of place.

“If they get their way, it will be the owners giving two fingers in stone to the Heath, the people in the Heath and the council.”

Since launching the campaign to save the house, the Highgate Society has amassed support from more than 1,100 people.

The property – built in 1870 – was sold in 2000 to developers who were given permission by the council to build luxury flats on the grounds provided they restore the house. Having developed the flats they sold the property to an anonymous owner in 2005.

The new owner – believed to be a billionaire from the Middle East – submitted plans to bulldoze the house and replace it with an £80million mansion.

The society is adamant the current owner should abide by the existing planning agreement to restore the Victorian house.

Martin Adeney, from the Highgate Society, said: “This is a view loved by thousands who use the Heath and if it gets built you’ll have to turn your face away.”

Objectors need to contact Camden Council’s planning department before the deadline of December 31.

Responding to the concerns raised by campaigners, a spokesman for Athlone House said: “It is unrealistic to expect the new owner to implement the existing planning consent given the very poor condition of the building and the need to provide a very high quality living environment to meet today’s standards.

“The planning inspector accepted this reality and concluded that a new house would be acceptable subject to a high standard of design, which we believe [architect] Robert Adam has produced.”