Boris Johnson has warned of even stricter restrictions to deal with a surge in Covid cases caused by the new, fast-spreading disease.
More than three-quarters of England are now under Tier 4 – the strictest level ever imposed.
However, fearing a Level 5 lockdown, even more draconian measures could be on the way in the next few weeks.
Mr Johnson said he was “completely reconciled” with a likely tightening of anti-Covid measures.
He said that while the existing tier system is already “very tough,” it probably needs to be taken to a new level.
The Prime Minister told BBC1’s Andrew Marr Show: “We may have to do things over the next few weeks that are getting more difficult in many parts of the country. I totally agree.”
“There are obviously a number of tougher measures we would need to consider.
“I’m not going to speculate now about what they would be, but I’m sure all of our viewers and listeners will understand what the kind of thing is … clearly school closings that we had to do in March are one of them these things. “
Mr Johnson said a mass vaccination program was the way out of the tiering system.
He said, “What we’re doing now is the tiering system, which is a very tough system … and unfortunately it’s probably going to be more difficult to keep things under control. But we’re going to check it out.”
He added, “And we have a prospect of tens of millions of dollars in vaccines.
“And that, I think, is something that should keep people going on your October show in what I predicted. It’s going to be a very bumpy time right now. It’s bumpy and it’s getting bumpy.”
The comments came as Liverpool Council Presidents called for another national lockdown to deal with a new strain of Covid-19 and prevent a “catastrophe”.
The city’s incumbent mayor, Councilor Wendy Simon, and the Labor City Council cabinet said “urgent action” was needed due to the rise in coronavirus infections.
The new strain of Covid-19 transmits faster and is most prevalent in London and the South East, where hospitals are congested.
And Professor Sir Mark Walport, a member of the Scientific Advisory Group on Emergencies (Sage), said it was “pretty clear” that tighter restrictions were needed.
When asked whether Tier 4 measures are sufficient, the former chief scientific adviser said: “It’s the Tier 4 restrictions, they obey them.
“It’s about breaking through essentially every possible transmission path that we possibly can.
“Those are the things that are absolutely necessary and it is pretty clear that we will need more.”