Families sharing Christmas dinner create “perfect conditions” for coronavirus to spread, a professor of psychology has warned.

Professor Stephen Reicher, from the University of St Andrews, told Times Radio on Saturday: “Christmas is a gift to the virus.

“If you want the perfect conditions for the spread of the virus it would be to be indoors, somewhere that wasn’t well ventilated, somewhere which was crowded, somewhere where there’s alcohol so that we forget our inhibitions, and that describes perfectly the Christmas dinner.”

His comments came on the last weekend ahead of the planned temporary easing of restrictions over the Christmas period.

The latest figures from the Scientific Advisory Group for Emergencies (Sage) showed the reproduction number, or R value, of coronavirus transmission across the UK is estimated to have risen to between 1.1 and 1.2.

Prof Reicher, who sits on the Scientific Pandemic Insights Group on Behaviours (SPI-B), which advises Sage, added: “Of course we don’t want to give gifts to this virus, we want to look after ourselves, and the best way of doing that, I think, is sadly to postpone if we can.

“I recognise that for some families it does make sense to meet up – I mean, if you’ve got an elderly relative who might not see another Christmas or somebody who’s suffering greatly, there will be exceptions.

“But if we turn the exception into the rule and if many people meet, then we really are heading towards a disaster.”

He argued that it was important to limit the number of households that could meet up, with five days of relaxed measures over Christmas being “too long”.

Prof Reicher also warned about the consequences of people from different parts of the country, with varying levels of the virus, travelling to mix together.

He said: “The real problem here is, of course, that if you mix everything up – mix up high levels and low levels (of infection) – then you reseed the infection in areas that it is not as prevalent in and you just relaunch the pandemic.”