The UK will offer a round-the-clock vaccination program as soon as the doses are available, says Prime Minister Boris Johnson, with the plan to give the jab to 14 million people by mid-February.

Johnson has also refused to rule out further restrictions in England if the level of new infections is not brought under control, amid fears that the National Health Service could be overwhelmed.

The government has faced public criticism for the pace of its vaccination program, with calls to make the COVID-19 jab available 24 hours a day.

The prime minister has now said that as the roll-out is ramped up and more doses become available, mass vaccination centers will operate 24 hours a day.

The government has pledged to vaccinate almost 14 million people by mid-February and insists it is on track to do so. It must meet a target of two million vaccinations a week to meet its deadline.

Under the national lockdown people in England must stay at home and only go out for limited reasons.

There are still a variety of extra restrictions that could be introduced by the government. They include closing places of worship, banning outdoor food markets, making mask-wearing compulsory outdoors or restricting exercising outdoors.

But scientists are divided over whether tightening the restrictions even further would have a marked effect on bringing the R number, or reproduction rate of the virus, below one – meaning the infection is dying out rather than spreading.  

Johnson says the restrictions are "starting to show signs of some effect" but are under "constant review."

Opposition leader Sir Keir Starmer has said it is obvious more restrictions are needed. He accused Johnson of being "slow to act."

Meanwhile, Scotland has announced it will be tightening restrictions from Saturday. First Minister Nicola Sturgeon has announced sales of take away alcohol in some areas will no longer be allowed, "click and collect" purchases will be restricted to essential services, takeaway restaurants cannot allow customers inside to collect their food and it will reduce the categories of workers allowed to return to the office.

She warned that Scotland faces a "precarious and extremely serious" situation.