Prime Minister Boris Johnson will hold a Downing Street press conference at 5pm on Friday, No 10 said.

England’s chief medical officer Professor Chris Whitty and chief scientific officer Sir Patrick Vallance will also feature.

It comes as Downing Street said evidence currently suggests that the concerning new Brazilian variant of coronavirus may be more transmissible but does not affect vaccines.

The Prime Minister’s official spokesman said that scientists at the Government’s Porton Down research facility are investigating the new strain.

“As with some of the other variants we’ve seen, the Kent variant and the South Africa variant, evidence does suggest that it may be more transmissible,” he added.

“More research is required to confirm this and Porton Down will conduct that research but current evidence does not suggest that the strain causes any higher mortality rate or that it affects the vaccines or treatments.”

Travellers from across South America have been banned from entering the UK.

The ban, which also covers the Central American state of Panama and Portugal – due to its strong travel links with Brazil – and the former Portuguese colony of Cape Verde, came into force at 4am on Friday.

More follows.