Andrew Lloyd Webber has said he is determined to open his theatres on 21 June, even if he risks being arrested.
The impresario's West End production of Cinderella is scheduled to begin previews on 25 June, four days after so-called "freedom day".
"We are going to open, come hell or high water," he told the Telegraph.
The government has said it will make a judgement soon on whether to proceed with the lifting of lockdown restrictions on 21 June.
According to reports, that date may be pushed back by the government due to concerns over the impact of Covid-19 variant.
Theatres are currently able to operate with with reduced capacities and socially distanced audiences.
Lord Lloyd-Webber has previously insisted that productions like his large-scale musicals are "impossible" under those restrictions.
The 73-year-old told the Telegraph he is prepared to be arrested if authorities try to intervene in his reopening plans.
"We will say 'come to the theatre and arrest us,'" the Evita and Phantom of the Opera composer is quoted as saying.
The theatre mogul said he may have to sell his six West End venues if the government does not relax its restrictions.
The pandemic has had a catastrophic financial impact on the theatre industry and many have remained closed despite the ease in Covid-19 measures.
"If the government ignore their own science, we have the mother of all legal cases against them," Lord Lloyd-Webber continued.
"If Cinderella couldn't open we'd go, 'look, either we go to law about it or you'll have to compensate us."'
'We can open safely'
Speaking to Radio 4's Today programme on Wednesday, he called on the government to stop "penalising" the live music and theatre sector.
"We can open safely," the impresario insisted. "Please, please let us get open."
He claimed that recent pilot events had shown there was "no chance of infection being passed... provided certain protocols are maintained".
The government has yet to publish the results of its test event programme, which included having a live audience at last month's Brit Awards.
Audience members at the Brits, held at London's O2 arena, were not required to wear masks or socially distance as they had all been required to take a Covid test.
Lord Lloyd-Webber said he was happy for his audiences to wear masks at his shows and for so-called vaccine passports to be used.
He said he had spoken to "leading counsel" who had told him it would be "neither rational nor proportionate" for the government to "stop us from going forward."
"My feeling is I've gone through everything with the counsel," he continued. "I've gone through [everything] about the theatre itself, which has no recirculated air, the incoming air passes through filters completely.
"There are 30 places in the theatre where the spread of air comes from. I'm not a mechanic, but we have the CO2 [carbon dioxide] monitoring that shows that the air is purer in there than it is outside."
An organisation representing venues that open at night, such as pubs, nightclubs and live music venues, has said it is also considering taking action should the government delay its lockdown relaxing measures.
"The decision to delay will leave us no other option but to challenge the government aggressively," said Michael Kill, CEO of the Night Time Industries Association (NTIA).
'We have to abide by the rules'
Cinderella was due to open last August but is now scheduled to have its opening night at the Gillian Lynne Theatre on 14 July.
Lord Lloyd-Webber also has plans to re-launch his West End productions of The Phantom of the Opera and Joseph and the Amazing Technicolor Dreamcoat.
Communities secretary Robert Jenrick said on Wednesday he "completely sympathised" with the impresario and those in the theatre sector.
"We want to get them open, we are doing pilots," he told Sky News. "We want to get those theatres open so great new productions like Cinderella can open.
"But you have just got a few more days to wait until the judgment that the Prime Minister is going to make on the basis of the data."
When asked if Lord Lloyd-Webber should be arrested if he does open theatres without restrictions relaxing, Mr Jenrick said: "We all have to abide by the rules."
Julian Knight, the chair of the DCMS (Department for Digital, Culture, Media and Sport) Committee said: "It is very frustrating for the live events industry as we can see from Lord Lloyd-Webber's comments though clearly I wouldn't support anyone breaking the law.
"With the 21 June reopening on a knife edge the government needs to be absolutely upfront about the results of its pilot events and how they feed into decision-making."
Lord Lloyd-Webber is the owner of seven London theatres, one of which he is currently in the process of selling.