His intervention came as the Scottish Government pledged to match Boris Johnson in England by offering a vaccine booster to all adults by the end of next month to help slow the spread of the omicron variant.

Nicola Sturgeon disclosed on Tuesday that “urgent modelling work” was underway on how to expand Scotland’s booster rollout programme, with two million Scots on the waiting list following this week’s huge expansion in eligibility.

But she provided no deadline for the rollout to be completed or any indication of how the expansion would be achieved. Hours later Mr Johnson unveiled a detailed blueprint for England that included the Jan 31 deadline.

Ms Sturgeon last week backed down on her threat to extend vaccine passports to pubs, restaurants and theatres before Christmas after her Government admitted the scheme had little if any impact on encouraging people to get jabbed.

However, earlier this week she said Scots should take a Covid test every time they go out to meet someone from another household, including doing their Christmas shopping or meeting friends and family for dinner.

‘We should all have a version of Covid certification’

Prof Leitch told Times Radio: “Our tone is now, if you are going to meet people outside your household, test. We should all have a version of Covid certification without the law telling us to Covid certify.

“So I’m going to have Christmas dinner with my sister and her husband and my mum and dad.

“I’m not going to check their certificate at the door before my mum comes for turkey, but she is 81 and she will do a Covid test, she will do a lateral flow test before she comes, she’s had her booster and I can be as certain as I can that the environment I’m bringing her into is as safe as I can make it.

“That doesn’t mean we’re not going to have Christmas dinner and we’re not going to have a fun day but she will Covid certify before she comes.”

The Joint Committee on Vaccination and Immunisation (JCVI) this week recommended that the booster programme be dramatically widened to all adults instead of only the over-40s.