The UK's five-day Christmas bubble plan will "pour fuel on the Covid fire" and lead to more deaths, a SAGE member has warned.
Professor Andrew Hayward said the four nations' approach to Christmas risks triggering a third wave of the pandemic in the new year.
Earlier it was announced that three households will be able to mix indoors from December 23 to 27, regardless of existing lockdown tiers.
The rules mean families could be reunited for the festive season, although they cannot meet in pubs and care home residents over 65 are not included.