Under the post-lockdown guidance, pubs in Tier 2 areas can only stay open if they can function as a restaurant, and alcohol can only be served with a substantial meal.
The "no lingering" warning was issued by the Prime Minister's official spokesman, who said customers could no longer stay "once the meal is finished".
The Local Government Association (LGA) has suggested a two-hour turnaround is the "maximum amount of time for a meal of multiple courses".
Its guidance has endorsed the Number 10 edict that "enforcement will be targeted at those premises which are clearly stretching things too far by allowing customers to stay well beyond the duration of a meal and in effect facilitating longer drinking sessions".
It will be seen as a further imposition on hard-hit pubs, with the Beer and Pub Association estimating 14,000 of the 21,000 pubs in Tier 2 areas will remain shut because they cannot serve meals or do not believe it is financially viable to open.
Nick Griffin, the chief executive of the Licensees' Association, said there were still "ridiculous" anomalies that allowed a family to go into a pub and order two coca colas for their children but no food because the regulations only covered the sale of alcohol.
A cheese sandwich was also technically not a "substantial" meal, but taking the cheese out of the bread and putting it alongside it with some salad and chutney made it a "substantial" ploughman's lunch, said Mr Griffin.
"Without clear central guidance, it passes back to local authorities in many respects," he added. "With the best will in the world, without guidance they will judge things in a myriad of different ways. Some have been far more understanding than others."
Both the Licensees' Association and the British Beer and Pub Association fear the Christmas relaxation to allow three household bubbles to stay together for the festive five days could backfire on the industry.
Although the bodies believed three households could each book a table separately at a pub in order to eat out "together" while keeping a social distance and not mingling, both felt the complexity and publicans' fears of a breach would make it virtually impossible.