Jermyn Street Theatre in London will remain shut until 2021 due to a lack of information about the reopening of venues from government.
Last month the theatre was saved from closure with an emergency grant from Arts Council England.
Artistic director Tom Littler said: "Even if we are allowed to reopen, British theatres cannot break even with social distancing – we rely on full houses.
"Theatres in Europe are already reopening – because, for example, there’s more state funding for theatre in Berlin than in the whole of England, so they can run with socially distanced audiences."
He added: "Theatres have asked government for a rescue package – a mix of loans, insurance, tax breaks, the extension of the job retention ’furlough’ scheme, and an investment. The money we need is far less than the bailout of the big three airlines.
"Week after week has gone by. Government silence has been deafening."
Littler said the industry is "falling apart" and warned the "only risk bigger than being closed [is] reopening and being forced to close again".
He added: "I’m entirely confident theatre will return, as it has endured for thousands of years. Gathering to witness live drama is a one of humanity’s oldest activities.
"But the survival of the theatres we know and love is directly in the government’s hands. It is not a question of when, but if.
"Without government investment, it will take decades for theatre to crawl back to anything like its current levels. While we wait, the next generation of artists will be forced out of the industry."
Littler urged theatre fans to write to their MPs and sign a petition for more support for the arts, which is being debated in parliament later today (June 25).
The artistic director also urged people to donate to the Jermyn Street Theatre via an online GoFundMe page.