According to reports, City Hall believes that Tier 3 measures – the “worst possible scenario” potentially lasting months – will need to be introduced without the imposition of countrywide rules.
Sadiq Khan, the mayor of London, has repeatedly urged the prime minister to follow the advice provided by the Scientific Advisory Body for Emergencies and implement a time-limited lockdown across England.
It comes as the government continues to defend its regional approach to the virus, despite becoming increasingly isolated. Earlier this week, amid a resurgence of infections, both France and Germany announced national lockdown measures.
A City Hall source told the Evening Standard: “If government does not bring in a circuit breaker, it is highly likely that Tier 3 restrictions will be brought to London in the coming weeks, and then a longer lockdown might well be needed."
They added: “We know that when it comes to this virus acting early and decisively is best, both for public health, but also for the economy. The more we delay in implementing measures, the more stringent they need to be and the longer they have to be in place.
“The mayor is clear that with cases, hospitalisations and death rising across the country since August, the government should have listened to the advice of Sage and introduced a short circuit breaker.
“Ministers must ask to bring in a circuit breaker before it’s too late and the country is plunged into a deeper health crisis with a longer lockdown needed.”
However, the power to implement a higher level of restrictions ultimately lies with Mr Johnson and a government source told The Independent “nothing is imminent” regarding London.
The capital moved to Tier 2 level restrictions two weeks’ ago, which includes a ban on household mixing indoors, including pubs and restaurants, unless with a “support bubble”.
In the highest level – Tier 3 – people are also banned from meeting other households in most outdoor public venues or private gardens and pubs and restaurants are only allowed to serve alcohol alongside a “substantial” meal.
As it stands, the highest restrictions currently apply to Greater Manchester, Lancashire, Liverpool City Region, Nottinghamshire, South Yorkshire and Warrington.
On Thursday the NHS Test and Trace system recorded its highest-ever weekly number of positive cases, while a study by Imperial College London found almost 100,000 people are catching Covid-19 every day.
The latest data from the test and trace system shows that a total of 126,065 people tested positive for Covid-19 at least once in the week to October 21 - a 23 per cent increase on the previous week and the highest weekly number since the programme began at the end of May.