Hospital workers take part in a protest in London on April 28, 2020, calling on the government to provide personal protective equipment for all health workers. (Matt Dunham/AP)

LONDON — British Prime Minister Boris Johnson returned to work to find his government under mounting pressure to explain why front-line workers for the National Health Service were donning garbage bags and makeshift masks to protect themselves against the coronavirus during the pandemic.

A BBC “Panorama” special investigation that aired Monday charged that the government had failed to include crucial personal protective equipment, including gowns and face shields, in its pandemic stockpile. The show — titled “Has the government failed the NHS?” — focused on the lack of preparedness that has left health-care workers vulnerable to coronavirus exposure.