Andrew Lloyd Webber's company has sought to reassure fans after photos of shows at the London Palladium sparked questions about safety measures.
Audiences on Sunday and Monday were pictured wearing masks and separated by empty seats - but some felt the theatre was too crowded to be fully Covid-safe.
Critic Mark Shenton, who attended one of the events, said he believed "social distancing was not complied with".
But LW Theatres insisted there was at least 1m space between all parties.
"Social distancing was and is at the heart of all planning of events," chief executive Rebecca Kane Burton wrote on Twitter.
She added that "tens of thousands" of pounds had been spent on ensuring there was a "bubble" around each party. The 2,200-capacity Palladium was "operating at around 50% capacity", LW said.
The photos that circulated online were taken at a musical called Songs For A New World on Sunday, and a Q&A with football manager Arsene Wenger on Monday.
Shenton, who posted images on Twitter from Sunday's show, said the "seating wasn't even staggered... so I'm not sure this was really safe".
He wrote: "I didn't have my tape measure with me last night, but I'd like to see proof that there was 1 metre distance between myself and the two women seated directly in front of me (who kept their masks off for much of the show to eat crisps!)"
He added: "On the other hand, temperature checks were made, mask wearing was properly enforced; staggered arrival times meant less crush to get in, and bar service was entirely by seat delivery service. So @LondonPalladium was doing its best. But seating was NOT socially distanced enough."
"Unfortunately I felt the same," replied theatre blogger Musical Manda. "As a result I won't be seeing my parents for a week."
Many other people on social media, including TV presenter Piers Morgan, queried why such audiences were allowed in theatres but not football stadia.
He wrote on Twitter: "How can the London Palladium be packed like this last night for an event with Arsene Wenger, but football fans aren't allowed to watch matches outside even socially distanced?
"I'm completely bemused."
'It was not rammed'
Other audience members did not share their concerns, however. The Guardian's critic Mark Lawson praised the "bold, Covid-safe show".
Theatre blogger Sarah McPartlan said on Instagram: "There have been photos shared that do make it look like the auditorium was rammed. Let me assure you that was not the case. I felt like I was quite far from anyone else in the audience."
She posted her own photo from the royal circle, showing white markings on chairs where the audience was not permitted to sit.
Anthony Kerr, who queued in the rain to see Wenger, told BBC News: "In my opinion the London Palladium put on a safe event. There was a large crowd but we were 2m apart. And when we left they filtered people out in rows, there was no bottleneck."
Others said they had been put off going to the theatre after seeing the images online.
"I've been to the @_bridgetheatre where seats where removed and there was enough distance plus obligation to wear a mask and I felt totally safe there," wrote actor Toby Stephens in response to Shenton's photos. "But big theatres like this? I don't think so right now."
"It is so important to be safe," added Ray Rackham, artistic director of the London Theatre Workshop. "The last thing anyone wants is for a super spread to occur at an arts event; it will mean future events won't happen; and the already decimated industry won't survive much more."
In a statement, LW Theatres said this week's performances were "fully in line with and indeed go further than the government's current Stage 4 guidelines for the re-opening of theatres".
It added: "With the support of public health officials, Westminster Council and DCMS, we have a 1m distance plus safety mitigations - for example mandatory face coverings - social distancing between each customer bubble across The London Palladium, operating at around 50% capacity.
"We have ensured that all audience bubbles are seated at least 1m apart through the following reconfigured seats: in the circles, we use 'chequerboard' seating and, in the stalls, we have respaced rows to ensure a 1m distance on all sides."
The theatre was being deep-cleaned regularly, with "full decontamination fogging treatments", the company added.
2m or not 2m?
Government guidelines say theatres should "ensure appropriate social distancing". They say: "Where you cannot stay 2m apart you should stay more than 1m apart, as well as taking extra steps to stay safe." Extra steps include face coverings and good ventilation.
Guidance from the Society of London Theatres says: "Wherever possible you should keep people 2m apart. If this is not viable, keeping 1m apart with robust risk mitigation is acceptable."
"The key point there is 'viable' isn't it?" said Julian Knight MP, chair of the House of Commons culture select committee.
"The truth of the matter is, with 2m social distancing, you're probably looking at a capacity of 10-15%, and frankly it is completely uneconomic in every single way at many theatres to do 2m," he told BBC News.
Issues would arise with reopening theatres because "no-one gets everything right first time around", he said.
"When it's pointed out, these issues must be addressed because it's about building confidence in the system.
"At some point we're going to ask substantial numbers of people to go back into a darkened space with strangers to have a live experience. Because if we don't do that, the lights are going to go dark on many theatres throughout the country.
"They need to address this for that reason and ensure social distancing rules are followed to the letter. But at the same time this shouldn't make us put the brakes on."