Tough new coronavirus restrictions for London have moved closer after Downing Street refused to rule out a fresh crackdown.

As mayor Sadiq Khan signalled new curbs were likely in “the next few days”, Boris Johnson’s official spokesperson said the government would “not hesitate to act” on any rise in admissions to hospitals and intensive care units.

The capital is currently in the “tier 1” or “medium risk” category created by the government, but will soon be moved into the “tier 2” or “high risk” category that will ban separate households from mixing indoors and in pubs and restaurants, Khan suggested.

The mayor said it was “inevitable” that the shift would happen and said the “trigger point” would be when London moved past 100 Covid cases per 100,000 of population. As of Tuesday, that figure was 68.9.

The government said decisions were made about local lockdowns using more than just the infection rate.

Sam Tarry, a Labour MP in London, went further and called for a two-week “circuit break” for the whole capital that would shut pubs, restaurants and other businesses as in Scotland.

The PM’s official spokesperson said: “There’s a process for considering whether further measures are needed in all parts of the country and I don’t think it would be appropriate for me to pre-empt that.

“We look at a wide range of different data and take advice from the Joint Biosecurity Centre and local health officials on the ground, so we look not only at infection rates but also the rate of positive tests, admissions to hospitals, and admissions to intensive care units.

“We continue to closely monitor the data in all parts of England and I think we have shown that if it’s judged additional measures are necessary we haven’t hesitated to act.”

Khan has said it is inevitable the capital will pass a “trigger point” to enter the higher tier 2 coronavirus restrictions in the “next few days”.

London is initially expected to be put on the “medium” risk level on Wednesday, meaning no new restrictions would be imposed immediately and the rule of six and the 10pm curfew would stay in place.

But Khan told Sky News: “Across our city […] the average over the last seven days is about 90 per 100,000.” It is in fact slightly under 70, as noted above. Khan added: “All the indicators I have – hospital admissions, ICU occupancy, the numbers of older people with cases, the prevalence of the disease, the positivity – are all going the wrong direction.

“Which means, I’m afraid, it’s inevitable over the course of the next few days London will have passed a trigger point to be in the second tier.”

The mayor insisted London should move as a whole into higher restrictions rather than borough by borough, despite variable rates of infection across the capital.

“We’re keen to go as one, as we can see the complexities and the confusion caused by some boroughs having additional restrictions and other boroughs having less,” he said.

“Many Londoners work in one borough, live in another borough, study in another borough, go to a restaurant in another borough, so we’re really keen to go as one city.”

Groups of up to six people would still be able to meet outdoors in public spaces and private gardens if the capital were moved into tier 2.

Meanwhile, Ilford South MP Tarry has written to health secretary Matt Hancock to call for a “circuit-breaker lockdown” across London.

“Clearly this will mean that additional financial support needs to urgently be provided to all workers and businesses who will be affected,” he said.

“However, the cost of this support will be far smaller than that which will be required if infection and death rates soar and London is forced into a much longer lockdown to relieve the strain on our healthcare systems and prevent yet again suffering the worst Covid-related death toll in Europe as we saw during the first wave.”