LONDON, Dec. 15 (Xinhua) -- Another 18,450 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 1,888,116, according to official figures released Tuesday.

The coronavirus-related deaths in Britain rose by 506 to 64,908, the data showed.

The figures were revealed as the British government came under mounting pressure to reconsider its relaxation of coronavirus restrictions over Christmas.

In the latest development, leader of Britain's main opposition Labour Party Keir Starmer urged Prime Minister Boris Johnson to think again.

In a letter to Johnson, Starmer said that while he understood that people will want to spend time with their loved ones after an "awful year", the situation has "clearly taken a turn for the worse since the decision about Christmas was taken".

"It is my view that you should now convene COBRA (emergency meeting) in the next 24 hours to review whether the current relaxation is appropriate given the rising number of cases."

Despite a surge in coronavirus cases, the British government has decided to relax restriction rules for Christmas, between Dec. 23 to 27, allowing up to three households to get together in homes and places of worship.

Earlier Tuesday, the British Medical Journal and Health Service Journal said in a rare joint editorial that the government should "reverse its rash decision to allow household mixing and instead extend the tiers over the five-day Christmas period".

They said this would "bring numbers down in the advance of a likely third wave."

In response, the prime minister's spokesman said it remained the government's "intention" to allow up to three households to mix over Christmas, adding that the data will be kept "under constant review".

England is currently under a new three-tier system of coronavirus restrictions. The system, which put about 98 percent of England into the highest Tier 2 and 3, is due to be reviewed on Wednesday.

To bring life back to normal, countries such as Britain, China, Germany, Russia and the United States are racing against time to develop coronavirus vaccines.