Sadiq Khan is holding the Government to ransom by threatening to slash Tube and bus services unless Transport for London receives a financial grant today.
The Mayor of London said that without financial support, the transport body would be forced to "reduce the service we provide".
He warned that "today is the last day" to arrange a bailout and accused the central Government of "failing to give us the grant support we desperately need".
Mr Khan said: "Unless the Government today gives us confirmation of the grant that we need then the consequences could be quite severe and ramifications for all of us will be huge.
"So I’m hoping the government today agrees a grant for TfL to help us with us doing our bit to helping the virus but if they don’t I’m very concerned about the consequences going forward.”
Keith Prince, Conservative Transport spokesman on the London Assembly, warned that the mayor was “putting people’s health” at risk to “make a political point”.
Mr Prince said: “Sadiq Khan's ultimatum is unhelpful and alarmist and exactly the sort of political gameplay that no Londoner wants to see from their mayor during a crisis.
“Transport for London will inevitably need a bailout to continue operating during this crisis, but TfL has £1.2 billion in reserves which is enough to run the network for two months.
“Sadiq Khan needs to stop playing politics with people's lives.”
While former Conservative minister Stephen Hammond described Mr Khan’s comments as “extraordinary”.
He said: “He is threatening the health of Londoners by saying this sort of thing.
“We need to get the networks, the Tube and the London suburban network back up to full capacity."
Transport for London (TfL) is understood to be asking for a £2 billion state bailout, with Sadiq Khan warning the transport body's cash reserves were "running out". Mr Khan said TfL has beenin negotiations with the Government for around six weeks.
He told LBC: "I'm unclear about why the Government are waiting until the 11th hour to agree a deal. It is really bad form."
Downing Street said the Government is in discussions with Mr Khan over a "funding and finance package" for TfL.
The Prime Minister's official spokesman said Cabinet was briefed on Thursday about the negotiations, which were at an "advanced stage".
The spokesman said: "It is a commercial discussion. We remain in close contact with the mayor and TfL to look at how we can support them.
"Our priority is on reaching an agreement which keeps critical services running for those passengers who must use public transport to get work, ensuring we keep London moving safely.
"That means protecting key routes, rapidly increasing the number of services available and protecting the interests of taxpayers in the long term."