Playwright James Graham has said an "aggressive government bailout" is needed to save theatres from the impact of the coronavirus crisis.
UK venues have been shut for four weeks, with all West End performances cancelled until at least 31 May.
In several months' time, "all of the reserves will have dried up and there will be no money left", Graham warned.
"I don't even know if there will be a theatre or film industry that we can recognise when this is all over."
Graham, one of the country's leading dramatists, has turned his hit West End play Quiz, about the Who Wants To Be A Millionaire? coughing scandal, into an ITV mini-series.
'No middle ground'
While some theatres have started streaming online, he told the PA news agency it was "a collective artform".
He explained: "You need people around you to see it and do it and there is no middle ground now.
"If it's going to survive in any form it will need an aggressive government bailout and you either do or you don't do it. There is either theatre or there isn't any more.
"So there is kind of a clarity to what we need to ask government to do for it to survive and hopefully they will do it."
Graham's stage credits also include This House, Ink and Labour of Love, and he penned the TV dramas Brexit: The Uncivil War and Coalition.
"I am already exhausted about the scale of the fight ahead because every industry, every small business, are all in the same situation and it's obviously very upsetting," he said.
"But because the theatres were the first to close... probably, because of the very nature of what they are, gathering people together in close proximity, they will be close to being the last buildings to reopen."
Sir Andrew Lloyd-Webber recently said he does not expect theatres to reopen until the end of September.
Graham continued: "I am worried that to have the political argument to justify that level of arts investment again at a time when the economy will be devastated, that's difficult.
"I'm worried for what kind of work, what kind of artists, what kind of people, in a more dangerous climate, will be allowed to make the work.
"I think the default naturally goes to safety, rather than invention. I say this as a playwright who comes from a working-class background - working-class actors and artists might be the ones who struggle to find themselves back on those platforms and in those spaces."
'Considering further action'
A spokesman for the Department for Digital, Culture, Media and Sport said: "We are committed to supporting our theatres during this national emergency with help available through the government's unprecedented financial package for business, workers and the self-employed.
"We are in regular contact with the arts and culture sector as we work on our ongoing coronavirus response which includes considering further action that may be necessary."
Arts Council England has launched a £160m emergency package for venues, artists and workers across the culture sector.