The coronavirus lockdown tier system being used in England "was not very well thought out", a government scientific adviser has said.
Under current plans, a regional tiered system is set to replace the national lockdown when it ends on 2 December.
However, professor John Edmunds, a member of the Scientific Advisory Group for Emergencies (SAGE), has warned a return to the lowest alert level of the regional tier system, Tier 1, when the lockdown ends would be "very unwise".
"The problem with the tier system is Tier 1 doesn't do much at all, Tier 2 probably has some effect, but not a great deal, and Tier 3 seems to be able to hold the epidemic," he said.
"The problem with the tier system is that inevitably you end up with quite a lot of places with high incidence under those circumstances.
"Because the Tier 1 and Tier 2 ones just eventually drift up into Tier 3 with a high incidence, and then Tier 3 holds it there."
He added: "It wasn't a very well thought through strategy, frankly."
Prof Edmunds, of the London School of Hygiene and Tropical Medicine, also urged the government to use a long-term strategy when it comes to balancing the economy and the pandemic.
"We need to take a long-term view and be sensible and realise that we're going to have to have restrictions in place for some time," he said.
"Yes, we can lift them when it's safe to do so, which will be primarily when large numbers of people have been vaccinated.
"But flip-flopping between encouraging people to mix socially, which is what you're doing by encouraging people to go to restaurants and bars, versus then immediately closing them again, isn't a very sensible way to run the epidemic."
As of 9am on Saturday, there had been a further 26,860 lab-confirmed cases of coronavirus in the UK, slightly down from 27,301 on Friday.
Labour has also called for emergency legislation to "stamp out dangerous anti-vax content" following promising preliminary results from the Pfizer/BioNTech vaccine.