Sir Derek Jacobi said he was disappointed after an Orthodox synagogue was granted planning permission to extend its premises.
Last week, Camden Council approved a £12 million plan to redevelop the South Hampstead Synagogue in north-west London.
It involves more than doubling its size to create a four-storey building complete with a common room, café and men and women's seating on the same level to accommodate its 2,000 attendees.
The plans were opposed by 449 signatories, many of whom complained that it would lead to conjestion and noise pollution.
Sir Derek told the Ham & High newspaper: "Essentially, planning permission has been granted for a private social club with a synagogue attached. The area of worship, or 'church' part, is no bigger than the current size.
There's been a lot of scaremongering that goes beyond anything we're planning
"I have always valued Camden's ongoing commitment to equality, inclusivity, tolerance and progress, but I find it difficult to understand why Camden have approved the application for this non-inclusive multiplex, better suited to a city centre."
But Rabbi Shlomo Levin, senior rabbi at the shul, said: "There's been a lot of scaremongering that goes beyond anything we're planning. Our first task is to restore relations with the neighbours. We've always had relationships with the community and we're seeking to rebuild that and assure them that we'll be considerate neighbours."
He added: "We've outgrown the building. There are too many people to fit into the shul, into the hall, into the youth facilities. We're looking to bring in new youth services and expand our work in the wider community."
Around 670 people, including Labour peer Lord Levy, wrote to Camden council to support the planning application.