London Underground is set to be crippled on Tuesday because of a strike by thousands of workers amid a warning there could be no Tube services because of the action.
There will be a similar scale of disruption during a second walkout on Thursday, with a knock-on impact on Wednesday and Friday.
Members of the Rail, Maritime and Transport union (RMT) are taking action in a dispute over jobs, pensions and conditions.
Transport for London (TfL) said anyone whose journeys rely on the Tube should work from home if they can or consider different forms of transport.
TfL said there is likely to be no service on the London Underground network on Tuesday and Thursday.
A spokesperson for Mayor of London Sadiq Khan said: “The upcoming strike action will cause disruption to Londoners and businesses that are trying to recover from two devastating years.
“It will also damage TfL’s revenues at a time when TfL is already under huge financial strain due to the pandemic.
“TfL are working to mitigate the impact of the strikes but disruption is inevitable. The mayor urges Londoners who need to travel on March 1 and 3 to check before they make their journey, consider whether they are able to work from home and use alternative modes of transport where possible.
“Sadiq doesn’t want to see strike action and is imploring the unions to come to the table and work with City Hall and TfL.”
RMT general secretary Mick Lynch said: “Sadiq Khan knows that this raid on our members’ pensions and conditions is unfair and would lead to industrial action because he’s said it himself.
“Yet only last week we find out that the mayor has agreed to submit proposals to the Government that will result in attacks on those pensions.
“Which side is he on? The side of our members who risked their lives as key workers in Covid and are now, as he predicted, striking to defend (their) livelihoods and future? Or the side of a Tory Government which wants to attack jobs, pensions, conditions and services?
“The mayor can solve this dispute by agreeing to talks that meet the concerns of his own workforce.
“Our members are central to the future of passenger safety and confidence on the Tube and they’ll be at the heart of London’s recovery. For the good of his workers and London’s recovery, Sadiq needs to stand firm against the Government, stop the pensions raid and end the job massacre.”
Andy Lord, TfL’s chief operating officer, said: “I would ask anyone who needs to use the Tube on March 1 and 3 to check before they make their journey, consider whether they are able to work from home and use alternative modes of transport where possible.
“It’s highly unlikely there will be an Underground service running during the strike action and services are likely to be affected on the mornings of March 2 and 4 too.
“I apologise to customers for this and understand they will be frustrated by this strike action, but urge them not to take it out on those who are trying to help.
“We haven’t proposed any changes to pensions or terms and conditions, and nobody has or will lose their jobs because of the proposals we have set out, so this action is completely unnecessary.
“We know our customers deserve better than this and that is why we’re urging the RMT to talk to us so we can find a resolution to this dispute and call off this action, which is threatening London’s recovery from the pandemic.”
The strikes will lead to the closure of five London stations on Great Northern’s Northern City Line, from Drayton Park to Moorgate, because some are operated by London Underground.
On Tuesday and Thursday, Great Northern trains will be diverted at Finsbury Park into King’s Cross and won’t be able to serve the stations of Drayton Park, Highbury & Islington, Essex Road, Old Street and Moorgate.
Some may operate only north of Finsbury Park.
Southern, Great Northern and Thameslink trains around London are likely to be much busier than usual and journeys may take much longer generally, passengers were warned.