Gergely Karácsony, mayor of Budapest, has brought plans to a halt for The New National Gallery in Budapest's City Park, claiming that the project will have a detrimental impact on the environment.

Karácsony, who was elected on a green platform in October, said the Sanaa-designed structure was "such a monumental building that it would have an enormous impact on its environment," adding that while he isn't opposed to the planned gallery, he does oppose its planned location, City Park, calling it "one of Budapest's few and very precious green areas."

The €250m (£212m, $276m) gallery forms the cornerstone of the Liget project – a massive cultural redevelopment worth a reported €1bn (£851m, US$1.1bn), which has already included the renovation of Budapest's Museum of Fine Arts, the restoration of the Olof Palem House, and the opening of a storage and restoration facility for fine art.

Karácsony's proposal moved to prevent planned works on both the New National Gallery and the House of Hungarian Innovation, a €100m (£85.1m, $110m) project replacing the city's Museum of Transport, from going ahead. It was backed by Bugapest's General Assembly, led by Karácsony on 5 November.

At subsequent meetings with Karácsony, officials from the Hungarian government, including Prime Minister Viktor Orbán, demonstrated a willingness to listen to the mayor's concerns regarding the environmental impact of the gallery and agreed to halt construction, which was due to start in early 2020.

László Baán, a curator at the Museum of Fine Arts who spearheaded the Liget project, has hit back at the mayor's claims.

"The new buildings are not being constructed on green areas but are instead replacing parking spaces and long-outdated buildings planned to be demolished," he told The Art Newspaper.

In a statement, officials from the Hungarian government told Artnet News: "The Hungarian government continues to remain committed to Budapest projects to be implemented from state funds, provided that there is a consensus between the government and the metropolitan municipality regarding their realisation. The government is open to conducting a normal dialogue with the capital in the spirit of fair partnership, once the capital decides what it wants."