Health Secretary Sajid Javid will lead a Downing Street press conference as the Government faces pressure from health chiefs to impose coronavirus restrictions.
Mr Javid’s appearance comes amid mounting concern about rising cases and a faltering vaccination programme.
Matthew Taylor, chief executive of the NHS Confederation which represents health bodies, warned “we risk stumbling into a winter crisis” unless measures such as face masks and vaccine passports – the Government’s “Plan B” for the coming months – are introduced in England.
He called for ministers to come up with a “Plan C” of even tougher restrictions if those measures are insufficient to address pressure on the health service.
Ministers have rejected calls to introduce the contingency measures which were included in the Government’s autumn and winter strategy.
Downing Street said the number of hospital admissions and deaths are still “substantially lower” than they were earlier in the year.
“The important thing is the fact that our vaccination programme has been successful in breaking the link between cases and hospitalisations and deaths,” a No 10 spokesman said.
“Our focus remains on ensuring we get boosters out to those who are eligible.”
The spokesman added: “There isn’t any proposed plan for any further lockdowns. We are sticking to the autumn and winter plan we have set out.”
Business Secretary Kwasi Kwarteng said the Government does not “feel that it’s the time for Plan B right now” but suggested it was a “good thing” for people to wear masks voluntarily.
“I think people should do what they feel is the right thing to do,” he told the BBC. “They’ve got to, I think, be respectful towards other people, they’ve got to keep themselves safe and the public as well.”
England’s chief medical officer Professor Chris Whitty also stressed the importance of mask-wearing and encouraged people to take up the offer of a vaccination.
“Covid-19 cases are rising and winter is drawing closer,” he said. “Ventilation, masks in crowded indoor spaces and hand-washing remain important.”
The NHS Confederation is the membership organisation that represents the whole healthcare system in England, Wales and Northern Ireland.
Mr Taylor said the NHS is preparing for what could be “the most challenging winter on record” and urged the public to “show extra support for the NHS” by “behaving in ways that will keep themselves and others safe”.
He added: “It is time for the Government to enact Plan B of its strategy without delay because without pre-emptive action, we risk stumbling into a winter crisis.
“Also, health leaders need to understand what a ‘Plan C’ would entail if these measures are insufficient.
“The Government should not wait for Covid infections to rocket and for NHS pressures to be sky high before the panic alarm is sounded.”
Mr Taylor said if the Government “fails to get a grip” on rising coronavirus cases, the nation’s recovery from the pandemic could be “put at risk”.
The NHS Confederation’s warning came as coronavirus deaths in the UK rose to their highest daily level since early March, while cases are at their highest for almost three months.
On Tuesday, the Government said a further 223 people had died within 28 days of testing positive for Covid-19 – bringing the UK total to 138,852.
While the numbers are often higher on Tuesdays because of a lag in reporting deaths and cases over the weekend, this is the highest figure for daily reported deaths since March 9.
Meanwhile, the seven-day average for cases is standing at 44,145 infections per day.
Despite the success of the initial Covid-19 vaccination campaign, there are concerns in Westminster around the take-up of booster shots and jabs for 12 to 15-year-olds.
Mr Kwarteng told Sky News the slow uptake in this phase of the programme is “something that we really need to address”.
Just over 67% of the UK population has received two doses of vaccine, according to Government figures – compared with at least 75% in Denmark, 79% in Spain and 86% in Portugal.
Prof Whitty said “if you have not been vaccinated, now is the time” and “if you are offered a booster, please take up the offer”.
Prime Minister Boris Johnson said: “As we get close to winter, make sure you get a booster jab when offered to maintain your protection against Covid and keep your loved ones safe.”
When he appears in Downing Street at around 5pm, Mr Javid is expected to echo the call for increased vaccine take-up.