LONDON, June 24 (Reuters) - Andrew Lloyd Webber and other impresarios said on Thursday they had started legal action to press Britain"s government to publish research into the safety of holding indoor events during the pandemic. A joint statement from concert managers and theatre producers, also including Cameron Mackintosh and Sonia Friedman, said the industry had repeatedly urged the government to spell out its reasons for keeping restrictions on audiences in place. "We simply must now see the data that is being used to strangle our industry so unfairly," said Lloyd Webber "The Government"s actions are forcing theatre and music companies off a cliff as the summer wears on, whilst cherry-picking high-profile sporting events to go ahead. The situation is beyond urgent,” the theatre entrepreneur added. British authorities have conducted a pilot scheme in recent months, testing audiences at live events from soccer matches to the Brit Awards, to see if they can be held with full crowds. The producers said reports suggested the pilot events had gone well, but the government had "refused to publish the results from the first phase of the Events Research Programme, despite saying that it would do so on numerous occasions". A government spokesman said the research programme was still running. "(The ERP) is gathering important evidence to help get all live events, including theatre shows, festivals and gigs, fully back up and running once it is safe to do so," he added. The results would be published before the next stage in the government"s road map out of the restrictions, the spokesman added. That "Step 4" has been pushed back to July 19 from June 21 because of the spread of the more infection Delta variant. The pandemic initially forced all British theatres and concert halls to close their doors. Some briefly re-opened in December and, under Johnson"s roadmap out of lockdown, smaller productions resumed in May though at 50% capacity and with social distancing measures. Bigger musicals had been waiting for the wider lifting of restrictions. The joint statement from Andrew Lloyd Webber"s Really Useful Group, the LIVE music industry body and others also called for a government-backed insurance scheme to cover any cancellations of live shows over the summer and beyond. "A joint insurance scheme to protect us against another enforced closure is vital," Mackintosh said. "Opening without any sort of protection is impossible for many producers, live event organisers and theatre buildings across the country." Last week, Lloyd Webber said he would not take part in the pilot scheme but would comply with social distancing rules when his new musical "Cinderella" begins previews on Friday.