Rufus Norris has warned that the UK’s theatre industry is facing potential devastation as a result of the Covid-19 lockdown, that the National Theatre is “haemorrhaging” money and that some venues are days away from breaking point.

Norris, the National’s artistic director and joint chief executive, told the Guardian he was seriously worried about the future of Britain’s theatres and regarded the industry to be in the “premiere league of risk” because of its dependency on mass indoor gatherings. “I’m a natural optimist and I’m concerned because I don’t feel optimistic,” he said. “Unless there is a real and concerted drive to uphold the cultural industries in this country, it will be devastating. There is no point pretending otherwise.”

He called for government investment to avert disaster. “My biggest worry is about survival. I know several theatres that have days, not weeks. If the furlough scheme doesn’t continue, yet we stay closed as an industry, then it’s very hard to imagine how the sector will survive. I would like the government to increase and broaden the support of freelance artists who are suffering very badly.”

We contribute to GDP and the reputation of the country. That needs to be remembered

Norris, who has been ill – “I didn’t go to hospital but I felt pretty terrible for a couple of weeks” – said that while the health of the country was paramount, the creative sector must not be sidelined in the midst of this crisis. “There are many calls being made on government at the moment and the most important ones are for saving and protecting lives,” he said. “But two months ago we had a £110bn creative industries sector, including TV, film, dance and theatre, and it was the fastest-growing sector in the UK.

“We can genuinely claim to be world class. We contribute to GDP and the reputation of the country. That needs to be remembered as this wears on. The damage that will be done if we are not supported in this time is impossible to make up.”

Facebook Twitter Pinterest A cyclist rides past the National Theatre with its forecourt taped off to prevent use. Photograph: Isabel Infantes/AFP via Getty Images

Norris, who renewed his five-year contract at the National just months before lockdown, said the theatre had already furloughed 85-90% of its workforce and that this figure was still “evolving”.

He is “massively worried” about his theatre’s finances. “The National has a turnover of £100m a year,” he said. “It costs an awful lot of money for every day we are shut. No one knows when we can open again or when we can get back to a stable situation in which audiences feel confident inside auditoriums.”

There are “months” of reserve funds remaining in the theatre’s coffers, he added, which they are trying to make stretch to a year – “but when we have run out of reserves then what’s next is called insolvency.”

Not all of the theatre’s planned projects are still slated and although “only a handful” have been taken off the timetable, some of the decisions have come down to expense. Production budgets have been halved and there have been cuts to capital expenditure. “It’s really serious,” Norris went on. “We’re cutting everything as long as it doesn’t mean someone’s job.”

The theatre had planned to open Richard Bean and Oliver Chris’s Jack Absolute Flies Again next week; it was halfway through rehearsals when the theatre’s closure was announced on 16 March. The show’s set is fully built and docked, ready for use. “I think its subject matter will be very resonant – it’s set during the Battle of Britain – so I hope to reopen with it,” said Norris. Other shows such as Kate Tempest’s reworking of Philoctetes, Paradise, which was due to be staged in July, may be moved back significantly.

Norris hopes that theatres will be able to open by June or July, “but if we do not open this year – and we are planning each way as much as we can – it’s my job to ensure that the theatre survives this”.

Facebook Twitter Pinterest James Corden and Oliver Chris in One Man, Two Guvnors at the National in 2011. Photograph: Tristram Kenton/The Guardian

Norris said he felt frustration at the uncertain way that the closure of theatres was initially handled by the government: “I think this government does want to support and help and rebuild, but at the time I felt like it was a deliberate act not to take responsibility. In hindsight it was just clumsy, but it does leave you wary.”

Shortly after closure, Norris wrote about connecting with industry peers and putting competition aside. Theatres have continued to give each other support, he said, with the 13 largest regional theatres in daily contact with each other. He has had conversations with the producer Sonia Friedman and Bristol Old Vic’s artistic director Tom Morris this week, as well as keeping in regular contact with artistic directors including Rachel O’Riordan at Lyric Hammersmith, Rupert Goold at the Almeida and Indhu Rubasingham at the Kiln.

The National has launched a streaming scheme, offering some of its shows for free online viewing, which has had an astonishing degree of success, with more than 4m views across three productions. Norris sees this as confirmation that culture has a useful role to play in a time of high anxiety: “If people are very stressed, maybe it offers a balm and a relief.”

The programme started with One Man, Two Guvnors, starring James Corden, and it is set to stream Danny Boyle’s Frankenstein, starring Benedict Cumberbatch and Jonny Lee Miller, next week. But while Norris was heartened by the uptake, it is not an economically sustainable model for the medium; filming live productions is expensive and all the artists involved agreed to share their work for free, he said.

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“I’m sure there will be a surge of creativity,” he said of the current lockdown. “Historically it has been the case. It is Shakespeare’s birthday on 23 April; he wrote King Lear during the plague and afterwards in the restoration period there was explosion of energy.”

Norris added that Laurence Olivier, founding director of the National, might also have argued that the theatre’s formation came from a comparable situation, in the wake of the second world war: “Government encouraged theatres to put on serious works and not just entertainment.”