London's West End theatres need a £250m investment programme if they are to survive, a report has warned.
Some venues will not survive without investment, the report warns
The area's 40 commercially owned theatres require the cash over 15 years to refurbish outdated Victorian buildings, the Theatres Trust said.
Theatregoers would not put up for much longer with unsuitable venues built for audiences 100 years ago, it added.
"Without an investment, the prospects are bleak," the report's authors warned on Tuesday.
"The renaissance of the West End can only be brought about by refurbishing the buildings we already have," they said.
"Most theatre buildings still reflect the conventions of a period when theatre audiences were segregated into different classes, when decent conditions were only provided for a minority of the audience, and when theatre-goers were physically smaller."
Audiences could not be expected to tolerate such conditions, said the report.
"Sooner or later a major problem at one of the theatres will force a closure. The smaller playhouses will simply become too expensive to maintain."
Impresario Sir Cameron Mackintosh is building a new theatre
The Trust said most subsidised theatres had received National Lottery cash and there was now "a marked imbalance between the two sectors".
Some £48m is recouped each year by the Treasury from VAT on ticket sales, while customers spent about £789m in 2001 for tickets, transport, accommodation and restaurant visits, the report added.
Earlier this year impresario Sir Cameron Mackintosh announced he was ploughing £35m into redeveloping his theatres and building a new one, the Sondheim Theatre.