Rush hour commuters were crammed onto trains due to reduced services and station closures, sparking fresh coronavirus fears amid calls for Britons to stay home unless they have a critical job
London Underground staff were "furious" and key workers, including NHS nurses, expressed fears that they could catch Covid-19 while travelling to and from work.
Photos on social media show passengers packed onto carriages "like sardines" on the Tube, the c2c in Essex and other networks, as well as crowded platforms, long queues inside stations and crammed buses.
In some snaps, commuters are so tightly packed they are standing against each other or just inches apart despite Britons being told to stay at least two metres away from each other to prevent the spread of coronavirus.
The shocking images have led to calls for a "total lockdown" - and there are signs that one is coming soon - to force non-essential workers to stay at home.
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Amid falling passenger numbers and ticket sales, Britons who are still commuting to work vented their frustration and anger.
One commuter, who posted photos of queues at a ticket barrier at Walthamstow station in north-east London, tweeted: "Total lockdown NOW BORIS! Walthamstow 6am this morning! Stay Healthy... Stay Safe... Stay at home!"
A second wrote: "Reduced service equals packed Tube train."
Another commuter shared a photo of a packed train on the Hammersmith and City line in west London, writing: "So this is the self employed working class.
"On a 6:40 train from Upton Park going to Hammersmith.
"If 1 person on here has the virus then that will affect others, who will take that elsewhere. Lockdown needed."
A photo showed a crowded platform as workers prepared to board a Tube train at Colindale station, on the Northern line in north London, where a 15 minute service was operating.
The Twitter user who posted it wrote: "Where is my southbound train?
"I’m on the platform @colindale since 6 am and no sight of the train, platform is full of people, thanks for nothing!!!"
About 40 stations on the London Underground network have been or are due to be shut.
Outside the capital, train companies began running reduced services on Monday.
The Government has urged Britons to work from home and avoid travelling if it isn't essential, and indicated that tougher restrictions are on the way amid speculation that a total lockdown could begin this week.
Many social media users told how they continue to commute because they have a job that doesn't allow them to work from home or they feared financial hardship during the pandemic.
Others said their employers expected them in the office as usual and they had no choice.
Trains and buses are still running so that key workers - including NHS staff and people involved in food distribution - can get to and from their place of business.
But key workers have told how they are "terrified" of using public transport with so many others.
A Twitter user who identified themselves as a key worker shared a photo of a busy Piccadilly Line train, writing: "TFL has reduced the frequency of London Underground trains, which are now busier than they should be.
"Not much social distancing on the Piccadilly Line this morning."
Another person wrote: "We need to lock the city down! My partner and I are key workers, and terrified of travelling to/from work, the public aren't listening, non-essential workers still using public transport.
"The tubes are still packed!!! How can key workers stay safe???"
A nurse added: "So far I haven't seen the point of the @TfL reduced service & reduced carriages on the national rail services into #London.
"I'm a key worker (Nurse) and so have to go into work, currently packed into a very busy train, how is this encouraging social distancing? #COVID19."
A concerned husband posted a snap of a full carriage, writing: "7:40am on Monday on the Northern line and the tubes are packed.
"Beyond a joke. Please ban all but essential travel.
"My wife works for the NHS and this is what she had to deal with."
A Transport for London worker replied: "Sorry for the congested service.
"Our staff members are affected by the situation as well and we're urging all customers to follow the Government's advice and not make anything but essential journeys."
A man shared a picture of a busy station wrote: "Don’t think #London gets it @SadiqKhan @tfl @lbc why are there 4 carriage #trains running, tubes shouldn’t be packed, all these folk can’t all be key workers?
"If you still need to go to work it should be on yer #bike #cycle."
Another user wrote: "Colleague has just come to work by tube - because of reduced services, he says commuters were packed in like sardines. Come on @TfL - at least keep enough trains running during peak times!"
Finn Brennan, district organiser for train drivers' union Aslef, expressed alarm at services which were extremely busy despite advice aimed at slowing the spread of the coronavirus.
He wrote on Twitter: "Still heavy loading on some Tube lines this morning making social distancing impossible.
"This is endangering the health of the vital workers who have to use the system.
"The Government must act now to ensure only ESSENTIAL journeys are made.
"I'm being sent pictures of crush loaded platforms at some Jubilee line platforms this morning. Drivers and other frontline staff are furious."
Mick Cash, general secretary of the Rail, Maritime and Transport union, said: "There is still enormous personal pressure on the Tube workforce who are exposed to levels of social contact that the Government say are unacceptable for the wider public.
"The only people using our transport services should be essential workers who have to travel. Everyone else should stay away to protect themselves, the staff and the wider community."
Transport for London is urging people to only travel if their journey is "absolutely essential".
It has suspended the Circle line and Waterloo & City line, and reduced frequencies on other parts of the Tube network. Bus services have also been cut.
London Mayor Sadiq Khan, who reduced Tube services, has urged people not to leave their homes "unless you have a very good reason", and told them not to use public transport.
He said people must obey the guidance or others would die.
"This isn't advice, as far as I'm concerned. These are instructions and these are rules that we should all obey to stop people dying," he told BBC1's The Andrew Marr Show on Sunday.
TfL is running a reduced service to deter Londoners from travelling, but it means trains will be busier at times.
A spokesman urged customers to only use the network if their journeys are essential.
Train companies have slashed their timetables.
Photos showed crowded trains on the c2c network, which runs between London Fenchurch in the City and Shoeburyness in Essex.
A woman who posted pictures online wrote: "Good luck with social distancing for those having to travel on the c2c this morning."
An NHS worker wrote: “This train has less carriages than normal too so people are packed in and are standing 2 inches apart!”
Another passenger added: “The reduced timetable is a joke. The 6:31 from benfleet is packed!! I have 7 people standing next to me.
"There are no seats free because everyone is sitting next to each other. I have no choice but to go to work as I am NHS staff.”
Health Secretary Matt Hancock has suggested that NHS staff could be given free parking at hospitals, which may reduce public transport passenger numbers.
He told Sky News: "We are looking at that, actually. I can't make an announcement now.
"There are complications because you have got to make sure patients are able to park, but it is something that if we can find a way to do it, I would love to."
Meanwhile, rail franchise agreements are to be suspended to avoid train companies collapsing due to the coronavirus, the Department for Transport has announced.
Operators are being offered the chance to transfer all revenue and cost risk to the Government, and be paid a small management fee to run services.
Industry body the Rail Delivery Group (RDG) said it "strongly welcomes" the proposal.
The emergency measures will be in place for an initial period of six months.
The DfT added that the Government-controlled Operator of Last Resort (OLR) "stands ready to step in" for operators which do not accept the emergency measures.
This would effectively mean nationalising franchises.
