Boris Johnson refused to rule out a third national lockdown as coronavirus cases continue to rise across the UK.
The Prime Minister said rates of infection have increased "very much in the last few weeks", as pressure grows on the Government to do more to tackle the rise.
Northern Ireland and Wales are going into lockdown in the days after Christmas, and a senior emergency medicine doctor said the rest of the UK must do "whatever it takes" to get infections under control.
Speaking during a visit to Greater Manchester Mr Johnson was asked whether England would follow Northern Ireland in imposing stringent restrictions after the festive period.
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He said: "We're hoping very much that we will be able to avoid anything like that. But the reality is that the rates of infection have increased very much in the last few weeks."
Schools minister Nick Gibb earlier insisted England's tier system, which will see swathes of southern and eastern England move to the toughest restrictions, is "very effective".
But he added "we rule nothing out" when asked about the possibility of a national lockdown after Christmas.
The president of the Royal College of Emergency Medicine, Dr Katherine Henderson, described a "real perfect storm" for hospitals as they try to balance increased numbers of Covid-19 patients with non-Covid work and a lack of beds.
She told the PA news agency: "It seems to me we need to do whatever it takes to get the situation firmly under control so that we can vaccinate people and then move forward."
