The further easing of lockdown restrictions in England - due to come in this weekend - has been postponed for at least two weeks, after an increase in coronavirus cases.
Casinos and bowling alleys will remain shut, as Boris Johnson said it was time to "squeeze the brake pedal".
Face coverings will be mandatory in more indoor settings, such as cinemas.
England's chief medical officer, Prof Chris Whitty, warned the UK may have hit its limits on easing restrictions.
Appearing alongside the prime minister at a special Downing Street briefing, Prof Whitty said the "idea that we can open up everything and keep the virus under control" is wrong.
Asked whether it was safe for England's schools to fully reopen to all pupils in the autumn, he said it was a "difficult balancing act" but "we have probably reached near the limit, or the limits, of what we can do in terms of opening up society."
Speaking at the briefing, Mr Johnson said planned changes to guidance for those who have been shielding during the pandemic, and advice for employers, will still go ahead.
The rethink on easing England's lockdown follows new restrictions for people in parts of northern England, after a spike in virus cases.
The prime minister said progress in tackling coronavirus continues, with the daily and weekly number of deaths falling, but warned that some European countries are "struggling" to control it. The UK must be ready to "react", he said.
The ONS's estimates of daily cases - based on a sample of households completing swab tests - are higher than the figures for lab-confirmed cases reported by the Department of Health and Social Care (DHSC) because they include people without symptoms who would not otherwise have applied for a test.
Highlighting the ONS figures, Mr Johnson added: "The prevalence of the virus in the community, in England, is likely to be rising for the first time since May."
He said that with "numbers creeping up" it was time to "squeeze that brake pedal in order to keep the virus under control".