Health Secretary Matt Hancock has demanded more Tube trains run during the coronavirus pandemic to avoid overcrowding and infection, saying there is "no good reason" for the infrequent service.
Concerns have been raised about the number of people packing into London Underground trains after the timetable was reduced.
However Sadiq Khan hit back, with a spokeswoman saying: "TfL simply cannot safely run a full service because of the levels of staff sickness and self-isolation".
Boris Johnson declared the UK was on lockdown during a Monday night public broadcast and said only key workers and those making infrequent yet essential shopping trips should use public transport.
Mr Hancock said: “When it comes to the Tube, the first and the best answer is that Transport for London should have the Tube running in full so that people travelling on the Tube are spaced out and can be further apart – obeying the two-metre rule wherever possible.
“And there is no good reason in the information that I’ve seen that the current levels of Tube provision should be as low as they are. We should have more Tube trains running.”
Sadiq Khan’s office hit back, with a spokeswoman saying: “This is simply not true.
“The Mayor has told ministers countless times over recent days that TfL simply cannot safely run a full service because of the levels of staff sickness and self-isolation.
“Nearly a third of staff are already absent – there aren’t enough drivers and control staff to do it.
“The Government must act urgently to get more people staying at home rather than going to work unnecessarily – that means taking the difficult decisions they are refusing to take to ban non-essential construction work and provide proper financial support to freelancers, the self-employed and those on zero-hours contracts to stay at home.”
When TfL reduced train frequencies last week amid a drop in demand, it stated that this was “to ensure a safe and reliable service”.
Mr Khan took to Twitter earlier this morning and warned commuters that more lives would be lost if the public made unessential journeys.
“LONDON: I cannot say this more strongly: we must stop all non-essential use of public transport now,” he said.
“Employers: please support your staff to work from home unless it's absolutely necessary.Ignoring these rules means more lives lost.”
He added: “IMPORTANT: Growing numbers of TfL staff are off sick or self-isolating: we cannot run more services than we currently are.
“If you have to go to work, please don’t travel at rush hour - go at different times to keep contact to a minimum.”
NHS England said the UK had it’s biggest increase in coronavirus related deaths on Tuesday since the outbreak emerged.
A further 83 people have died, bringing the total number to 386.
Patients were aged between 33 and 103 years old and all were in vulnerable groups including those with underlying conditions.
As of 9am on Tuesday, a total of 90,436 people have been tested, with 8,077 positive results, up from 6,650 at the same point on Monday.
