The UK variant of coronavirus could be more deadly than the original, Boris Johnson has said.
Britain's Prime Minister said the latest scientific evidence shows the new variant has a higher risk of death.
"It is largely the impact of this new variant that means the NHS is under so much intense pressure," he said.
Professor Neil Ferguson, of the British Government's virus advisory committee, said the latest data showed up to 13 in 1000 people aged 60 who contract the variant strain could die, compared with 10 in 1000 who caught the original variant.
"It is a realistic possibility that the new UK variant increases the risk of death, but there is considerable remaining uncertainty," Prof Ferguson told ITV.
The new variant, of which there have been 29 cases detected in New Zealand's MIQ facilities, is also more transmissable.
Patrick Vallance, the British government's chief scientific adviser, said there is growing confidence that the variant is more easily passed on than the original coronavirus strain. He said it appears to be between 30 per cent and 70 per cent more transmissible.
British officials say they are confident that the vaccines that have been authorised for use against COVID-19 will be effective against the new strain identified in the country.
But Vallance said scientists are concerned that variants identified in Brazil and South Africa could be more resistant to vaccines, adding that more research needs to be done.
Britain has recorded 95,981 deaths among people who tested positive for the coronavirus, the highest confirmed total in Europe.
The UK is currently in a lockdown in an attempt to slow the latest surge of the coronavirus outbreak. Pubs, restaurants, entertainment venues and many shops are closed, and people are required to stay largely at home.
The number of new infections has begun to fall, but deaths remain agonizingly high, averaging more than 1,000 a day, and the number of hospitalised patients is 80 per cent higher than at the first peak of the pandemic in the spring.
- with AP