Three-quarters of pubs are staying closed because it is not worth opening in Tier 2, the industry's association has warned.
The British Beer and Pub Association (BBPA) said many pubs that had reopened after lockdown were already planning to shut again because trade was so dire under the stringent revamped tier rules.
A survey of operators representing more than 8,000 pubs, conducted by the BBPA between November 24 and December 2, found that just 27 per cent reopened following the end of lockdown.
It comes as the UK's four chief medical officers warned the new Covid vaccine will have only a "marginal impact" in the next three months.
On Friday, it also emerged the Covid 'R' number had fallen to its lowest level since August, dropping to between 0.8 and one compared to 0.9 and one the week before.
The majority of the country is currently in Tier 2, in which pubs and bars are not allowed to sell customers alcohol unless it comes with a "substantial meal". In the parts of the country under the stricter Tier 3 restrictions, pubs can only operate a takeaway service.
The harshest measures came into force in Wales on Friday, where pubs are now banned from selling alcohol and can only operate a takeaway service after 6pm. The ban prompted landlords to pour barrels of beer they will be unable to sell down the drain.
Emma McClarkin, the chief executive of the BBPA said it was "ridiculous" and "unfair" that stringent tier restrictions had forced pubs to remain closed during their most profitable part of the year after the industry had invested £500 million to make premises Covid secure.
She added: "It is just a shame so few are allowed to reopen and make a good go of it under the harsh new restrictions they now face. For those pubs that are reopening, some fear they could close again as soon as this week because they expect trade to be so low."
The Treasury has promised a £1,000 grant to aid all "wet-led" pubs, which generate most of their revenue from alcohol rather than food, during the tier period.
However, earlier this week the Government descended into confusion over its own pub rules as ministers clashed over what constituted a "substantial meal".
On Monday, Michael Gove prompted a backlash when he contradicted the Environment Secretary George Eustice's claim that a scotch egg would suffice. The Chancellor of the Duchy of Lancaster later backtracked and conceded the snack was sufficient to allow patrons to be served drinks.
On Friday, police were also accused of "over-zealous" enforcement of the rules, with reports of officers arguing with landlords over what qualified as a substantial meal and throwing customers out as soon as they had finished eating.
Tim Martin, the chairman of the Wetherspoon chain, lambasted the Government's "draconian" rules, which he said were "devastating" the industry and creating confusion for staff and customers.
"Many [pub managers] report that sensible explanations are impossible because the rules are so contradictory and absurd," he said.
A Government spokesman said: "We understand the pressure businesses are currently under, particularly pubs. These restrictions, which are reviewed on December 16, are essential so we can control the virus, protect the NHS and save lives.
"We have acted quickly to support businesses with one of the most extensive packages of financial support in the world worth £280 billion, including the extension of the furlough scheme, various loan schemes, a business rates holiday, VAT deferrals and grants of up to £3000 a month for those required to close."