No 10 has published data behind its decisions over England's new tier system as it tries to win MPs' support.
Downing Street's report said it sought to "balance the many complex impacts" of restrictions and keep them in place "for as short a time as possible".
It said allowing the virus to spread exponentially "would lead to impacts... considered intolerable for society".
But senior Tory MP Mark Harper said the "wheels are coming off the government's arguments".
MPs will vote on the plans on Tuesday.
The government announced its tougher three tiers to tackle the virus last week, with Boris Johnson telling reporters on Monday: "We can't afford to take our foot off the throat of the beast... to let it out of control again."
But a number of Tory backbenchers have threatened to vote against the motion when it comes to the Commons, including the Covid Recovery Group (CRG) of MPs - chaired by Mr Harper.
Labour leader Sir Keir Starmer said his party would abstain on the vote, saying he had "serious misgivings" about the measures.
But he said it was "in the national interest" to let the restrictions pass through the Commons without Labour's opposition to ensure some measures were in place.
A No 10 spokesman accused Sir Keir of "playing politics in the middle of a global pandemic, instead of working with the government to find a way through this difficult time for the British people".
England's current lockdown will end in the early hours of Wednesday 2 December and will see the country placed into one of three tiers: medium (one), high (two) and very high (three).
However, the majority of the country, over 55 million, will be under the strictest two sets of measures.
The announcement led to criticism from some Tory MPs, who were concerned about the impact in their constituencies.
Mr Johnson wrote to his party twice over the weekend to appeal for their backing and to grant some of the CRG's demands.
They included the publication of the data on the health, social and economic impact of the tiers, and the promise MPs could vote again on the measures in January - with the possibility the tier system could end on 3 February.
But the government report - published on Monday - said it was "not possible to forecast the precise economic impact of a specific change to a specific restriction with confidence".
The document is largely made up of information already available.
It said the challenge of balancing health and societal impacts was not straightforward, but the government would continue to pursue the best overall outcomes.
The chair of the Treasury select committee, Tory MP Mel Stride, condemned the report as "a rehashed document [that] offers very little further in economic terms".
He told the BBC he would support the government to ensure there were some restrictions in place, but added: "It's frustrating that there is little here that sets out how the different tiers might impact on the specific sectors and regions across the country.
"Those looking for additional economic analysis of the new tiered system will struggle to find it in this document."
The CRG chair, Mr Harper, said the report "seems to be collapsing under the glare of scrutiny".
He repeated accusations that the government's modelling on deaths and hospital capacity had been wrong, adding: "We have asked repeatedly for the information that vindicates these hospital projections and they have not been forthcoming."
While Labour will abstain, the Liberal Democrats have said they will not back the plan - although it is not clear whether they will vote against or abstain.
The SNP will abstain in the vote, as it only covers restrictions in England.
With many of the opposition MPs abstaining, it would take a huge Tory rebellion for the measures to fall, which is unlikely.
At first glance there doesn't appear to be much, if any, new information in this document.
The government's analysis draws on studies and data already in the public domain to try to assess the impact of the tiered system of restrictions.
So will it convince Conservative MPs sceptical about the need for tighter restrictions that they are, in fact, necessary?
Yes and no.
Some Tory backbenchers may be satisfied the government has at least attempted to provide further evidence that tougher measures are needed. They've made their point.
Others will flick through the 48 pages and discard it, knowing all along that without some elusive magic formula the government could provide, they would never have been convinced.
The government is likely to win Tuesday's vote, but as the pandemic wears on, it is having to go to greater and greater lengths to keep its own MPs on side.
Speaking shortly before the data was published, Mr Johnson said he "understood people's frustration" with the stricter tiers.
He said: "The tiering system is tough, but it is designed to be tough to keep [the virus] under control."
"What we can't do is forsake and abandon all the gains we have made now just when we are starting to see real progress in the science."
In the report, the government pointed to data from the Office for National Statistics, showing a rapid increase in people testing positive for the virus between September and November - from 59,800 a week to 633,000 a week.
It said the new "strengthened" tier system was "designed to keep R [the infection rate] below one so that prevalence continues to fall, the significant impacts of the virus are reduced, and so that, ultimately, fewer restrictions are required."
It added that a "stable and fully functioning health system is one of the pillars that underpins our society and our economy", with the government's view being "the severe loss of life and other health impacts of allowing the NHS to be overwhelmed would be intolerable for our society".
The document also pointed to the economic forecasts from the Office for Budget Responsibility - which were published alongside Chancellor Rishi Sunak's spending review last week - predicting the value of the economy will fall by 11.3% by the end of the financial year.
But, while the report conceded there would be "major impacts" on the economy from the restrictions, it added: "Any attempt to estimate the specific economic impacts of precise changes to individual restrictions for a defined period of time would be subject to such wide uncertainty as to not be meaningful for precise policy making".
Labour leader Sir Keir defended his party's decision to abstain on the vote for measures, saying it was "better that these regulations can be amended and put in place than if there are no regulations".
He said the "serious misgivings" he had included over the performance of the test and trace system and "real concerns" over the level of economic support for those in the highest tiers.
But, Sir Keir added: "Although the number of cases is coming down as a result of lockdown, the virus is still a significant risk and in principal we accept there is going to have to be continued restrictions."
However, one Labour MP, Richard Burgon, has already said he will vote against the tier system, arguing that it will fail to lower the infection rate and make another lockdown more likely.
Liberal Democrat leader Sir Ed Davey described the system as "chaotic" and said his party would not back the measures until the prime minister addressed their concerns - such as working with local authorities and supporting pubs.