RELAXATION of coronavirus rules for Christmas have been cut to just one day for York residents, the Prime Minister has announced. 

At today's coronavirus press conference, Boris Johnson said the rapid spread of the virus in many parts of the South-east of England is "now being driven by a new variant" - with a case rate doubling time of seven days in some areas. 

He added that Christmas cannot be continued "as planned" and Tier 3 and Tier 2 areas, such as York, can now meet up to three households on Christmas Day only. 

Meanwhile, London, The South East and the East of England will enter a new tier four-level from tomorrow - and must stay at home, with non-essential retail, indoor gyms and hairdressers to close.

Tier 4 residents should also stay local and not travel abroad over the next two weeks.

The governments Chief Scientific Adviser, Sir Patrick Vallance, said the new variant was first seen in mid-September in London and Kent. 

He added that by December it had become the "dominant variant" in London - and the new British strain could be up to 70 per cent more infectious than the existing strain currently present in the north. 

Data suggests the strain is thought to increase the R rate - the rate of transmission - by a further 0.4. 

However, Sir Patrick Vallance added that the variant increases transmissibility but not lethality. 

Boris Johnson said: "I know how disappointing this will be, but we have said throughout the pandemic that we must and we will be guided by the science.

"When science changes, we must change our response. When the virus changes its methods of attack we must change our method of defence and as your prime minister I sincerely believe there is no alternative open to me." 

Meanwhile, First Minister of Scotland, Nicola Sturgeon, has announced a strict travel ban from Scotland to the rest of the UK throughout the Christmas period. 

"People from Scotland should not visit other parts of the UK, or vice versa," she said.