The government's scientific advisers called for a short lockdown in England to halt the spread of Covid-19 last month, newly released documents show.
The experts said an immediate "circuit breaker" was the best way to control cases, at a meeting on 21 September.
Communities Secretary Robert Jenrick insisted the government had taken "robust action" that "balanced" the impact on the economy.
But Labour has described the documents as "alarming".
It comes as the Liverpool region prepares to enter a "very high" Covid alert level from Wednesday, the highest of a new three-tier system for coronavirus restrictions in England.
Every area will be classified as being on medium, high or very high alert under the system. It is not clear what the specific criteria is for each alert level.
Most parts of England are the lowest tier, but Essex has asked to be moved to "high" level restrictions.
Shielding is not being reintroduced in England yet, but people who were on the list will receive a letter with updated advice to avoid getting Covid.
Meanwhile, the latest Office for National Statistics figures showed there were 343 deaths involving coronavirus registered in the week to 2 October - a figure that has been doubling every fortnight over the last month.
At a press conference on Monday evening, Prime Minister Boris Johnson said the alert system for England could succeed in driving cases down if it was implemented "very effectively", and he rejected the "extreme route" of a full nationwide lockdown "right now".
But at the same briefing, England's chief medical officer, Prof Chris Whitty, voiced concerns over the impact of the new rules, saying he was not confident the "base measures" in the highest tier "would be enough to get on top of" the virus.
"That is why there's a lot of flexibility for local authorities [...] to do significantly more," he said.
Released shortly after Monday's press conference, minutes from the meeting of the Scientific Advisory Group for Emergencies (Sage) - which feeds into UK government decision-making - stated the advisers had called for the immediate introduction of a short national lockdown three weeks ago.
The papers also showed the scientists suggested:
- banning all contact inside homes with members of other households
- closing all bars, restaurants, cafes, indoor gyms and hairdressers
- requiring all university and college teaching to take place online
Of all the measures proposed by the advisory group, just one - advising those who can work from home to do so - was implemented by the government at the time.
In the documents, Sage warned that "not acting now to reduce cases will result in a very large epidemic with catastrophic consequences".
Speaking to BBC Breakfast, Mr Jenrick said the government had introduced measures such as the rule of six at the time, and stressed the Sage papers had contributed to the measures the PM announced on Monday.
He said they had taken "balanced judgements" that weighed up the effect on the economy and "all the other unintended consequences" of measures, such as the impact on mental health and delayed surgeries.
On the new three-tiered system, he said: "We are now able to have a very clear and consistent framework across the whole country, so people will be able to understand approximately what the rate of infections is in their own area and what the rules are accordingly."
He later told BBC Radio 4's Today programme that there were no plans for other parts of the country to go into the highest tier this week, but plans would be "kept under review".
Labour's shadow health secretary Jonathan Ashworth told BBC Breakfast he was "alarmed" by the Sage papers, and called for ministers to explain why the advice was "rejected".
He also insisted the government was going to have to go further than the latest measures, saying things were getting "really serious" as winter approaches.
Cases are increasing across the whole of the country and the number of people in hospital is now higher than before the full lockdown in March. We are at a critical stage in the epidemic.
It is at this moment the gulf between the official scientific advice and the decisions made by government has been laid bare.
It is the case that "advisers advise and ministers decide". When considering new measures to stop Covid, government must also take into account the harms they cause to our health and the economy.
But there is some concern the government is doing too little, too late.
And that we can either choose the terms for controlling the virus now, or wait and the virus will force our hand as it did with lockdown in March.
The newly released Sage documents also showed advisers said NHS Test and Trace was only having a "marginal impact" and this would "likely decline further" unless the system expanded to keep up with the rise in cases and people were given support to enable them to self-isolate.
A separate document from 17 September stated that Sage believed curfews in bars, pubs, cafes and restaurants were also "likely to have a marginal impact".
A 22:00 closing time was introduced for all hospitality venues in England from 24 September.
A Sage document from 21 September warned that "single interventions by themselves are unlikely to be able to bring the R below one" and both local and national measures are needed.
However, a document examining measures including a two to three week "circuit-breaker" - a short period of tightened restrictions - said this step, if it was "as strict and well-adhered to as the restrictions in late May", could "put the epidemic back by approximately 28 days or more".
"Multiple circuit-breaks might be necessary to maintain low levels of incidence," it added.
Most areas in England are in the medium alert level - meaning current restrictions continue, including the 10pm hospitality curfew and the rule of six.
Areas already under additional local restrictions are automatically in the high alert level - meaning bans on household mixing indoors are extended to include hospitality venues.
The city of Nottingham, which has the highest rate in the country, will start in this category alongside the rest of Nottinghamshire, East and West Cheshire and a small area of High Peak, as well as Greater Manchester, parts of South Yorkshire, and north-east England. Around 4.4 million people will be in high alert areas.
The Liverpool City Region - home to 1.5 million people - becomes the first area to enter the very high alert level, which - at a minimum - sees pubs and bars close if they do not serve "substantial meals", almost all household contacts banned and advice against travel. The rule of six will continue to apply in outdoor public spaces such as parks.
Areas in the highest tier are able to impose further restrictions, and in the Liverpool City Region this will mean the closure of betting shops, gyms, leisure centres and casinos.
Mr Johnson said he had agreed some of the measures with the region's Labour Mayor Steve Rotheram - but Mr Rotheram said that was "totally false" and that the new measures had been "dictated to us by the government".
The government has issued details of the full restrictions for each alert level.
Meanwhile, the Scottish government is drawing up its own three-tier framework of restrictions to be implemented later this month.
In Wales, a second national lockdown is being considered and First Minister Mark Drakeford has threatened a travel ban on people from English Covid hotspots if the prime minister does not impose his own.
Ministers in Northern Ireland's devolved government are meeting later to decide on further coronavirus restrictions.
A further 13,972 confirmed coronavirus cases were reported across the UK on Monday, with 50 more deaths within 28 days of a positive test recorded.
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