Updated: See the latest stories on the coronavirus outbreak.

One in three Transport for London (TFL) workers are off sick or self isolating amid the coronavirus crisis, London mayor Sadiq Khan has said. 

Despite the nation being placed under lockdown on Monday, sections of the London Underground have remained crowded at times with key workers forced to pack into tube carriages. 

Pictures of crammed trains have provoked widespread anger about a lack of social distancing, with the reduced number of trains blamed for overcrowding. 

There have been calls for the number of trains to be increased again, but Khan tweeted on Thursday to state that one in three TFL staff were off sick or self-isolating, writing “we cannot run more services”. 

The mayor also addressed a note to employers, writing: “staff must work from home wherever possible to help protect our key workers who need to travel.” 

In a later tweet on Thursday morning, Khan announced that early-morning tube use was down 13% compared to Wednesday, and bus use reduced by a further 8%.

On Tuesday Khan clashed with No. 10, urging them to close building sites across the city so construction workers didn’t have to travel on the Underground.  

Health secretary Hancock laid into Khan during a Downing Street press conference on Tuesday evening, claiming the Underground should be “running in full”, and there was “no good reason” for the packed carriages.

Many Tube services are now running every 10 minutes rather than every three or four, leaving passengers crammed together and unable to observe social distancing rules.