London Mayor Ken Livingstone has criticised council moves to cut funding for the Battersea Arts Centre (BAC).
The centre is located in Battersea's former town hall
Earlier this month Wandsworth Council said it planned to scrap the venue's £100,000 grant and charge £270,000 a year for rent and maintenance costs.
"If it carries out its threat, the cultural, social and economic benefits which the BAC delivers so successfully may be lost forever," said the mayor.
Mr Livingstone also attacked moves to close Wandsworth Museum.
"The museum is a highly valued and popular local resource for the community," he said.
The council has said cuts are necessary to make up a £5m deficit.
Located in Battersea's former town hall, the BAC has occupied its Grade II listed building on Lavender Hill since 1980.
Controversial musical Jerry Springer: The Opera was first performed there in 2001 and went on to be staged at the National Theatre.
National Theatre director Nicholas Hytner has joined calls to keep the centre open, saying its closure would be "a crushing blow".
"BAC is the vital, adventurous, creative well-spring of so much that is exciting about the theatre," he said.
"It has in recent years provided a whole generation of theatre makers without whom more established venues like the National would quickly atrophy."