The Central London Congestion Charge has increased to £15 per day from Monday.
Officials said the latest data shows that even with the charge back in place and many people still working from home, there are as many cars in the zone as there were before the lockdown began.
They added that analysis indicates that as the Government further eases restrictions, if those who would have used public transport instead choose to drive, car traffic levels in central London could double without any changes to the charge.
Mayor Sadiq Khan said: ‘The Government was absolutely clear that TfL must bring forward proposals to widen the level and scope of the Congestion Charge. Coronavirus continues to present our city with unprecedented challenges but I am determined to ensure that we emerge from this pandemic with a cleaner, greener and more sustainable transport system.
‘The reality is that due to social distancing requirements public transport can only carry a fraction of the number of passengers compared to pre-pandemic levels - even when we are back to running completely full services.
‘While capacity on the network needs to be preserved for those people who need it most, we can’t allow journeys that were previously taken on public transport to be replaced with car trips.’
Alison Cook, director of external affairs at Asthma UK and the British Lung Foundation, said: ‘As we start to recover from COVID, it's vital we don't see London's streets fill up with cars, which is why we support this action to encourage people to take more sustainable travel options. This must be alongside an expansion of the ULEZ, and action from all boroughs to support people to walk and cycle where possible.
‘For the sake of Londoner’s lungs, lets hang on to the cleaner air we have seen over the last few months, and keep pushing pollution levels even lower.’
Mr Khan is also extending the Congestion Charge reimbursement schemes to support those who could be most affected by the coronavirus pandemic or are part of the response.