Hundreds of suspected Covid outbreaks have been linked to offices in England over recent months - despite employers being told staff must work from home where possible.
New data from Public Health England (PHE) reveals more than 500 outbreaks are believed to have happened in offices in the second half of last year - higher than the entire retail and catering sectors put together.
A SAGE expert has warned that the chances of contracting the virus in poorly-ventilated offices can go up by 70 per cent.
Emergency service workers, manufacturers and mail delivery staff were also among those worst hit, PHE data shows.
The number of suspected outbreaks surged in October and November, the figures show.
Between June 29 and October 18, PHE were alerted to 1,530, and in just six weeks, between October 19 and November 29, nearly the same number, 1,426, were reported.
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And data released under the Freedom of Information Act reveals that in one week in December, there were 142 in all sectors.
Surprisingly, the figures show, offices accounted for 511 suspected outbreaks over these periods - with some workers saying they were not given an option by their employer.
In the same time frame there were 383 reported outbreaks across the entire retail sector, and 95 at restaurants and caterers.
The figure was higher for manufacturing workers, with 783 reported to PHE, while there were 115 on construction sites.
Police, fire and ambulance services reported 149 suspected outbreaks across England.
Between late June and the end of November, there were 21 linked to close contact services such as barbers and hairdressers.
Health chiefs have stressed that not all outbreaks have been confirmed.
The figures were initially obtained by the BBC.
Explaining why offices appear to be particularly badly hit, Prof Taylor, from the University of Strathclyde, said that they can be a "toxic" environment for coronavirus.
He said: "They have high occupational densities with little social distancing and are often sealed, with air con just recirculating pathogens like Covid.
"Hot-desking is commonplace and cleansing is hit and miss. It's a toxic combination."
And Prof Cath Noakes, who sits on the government's Scientific Advisory Group for Emergencies (Sage) committee, warned that poorly ventilated offices could see the chances of contracting coronavirus rise by 70 per cent.
Trade union the TUC has called for better protection for workers, especially since the more transmissible variant was detected in November.
General secretary Frances O’Grady said: “With new strains of coronavirus spreading like wildfire, workplace safety rules must catch up.
"We have a much better understanding of how people catch Covid-19 now than when the rules were written.
“Airborne transmission is the biggest danger. But little has been done to update safety rules in response.
"Too many workers are still in indoor spaces without adequate ventilation, or proper social distancing from other staff or customers.”
