With case numbers expected to rise in the coming days, Ms Sturgeon said she “fervently” hoped she would have “a normal Christmas with my family” and was not yet asking people to put festive plans on hold.

But she admitted she was not 100 per cent sure that Scots would be allowed to proceed with plans as she wrote to Boris Johnson demanding more funding for business support if she decided to reimpose restrictions.

In a joint letter with Mark Drakeford, the Welsh First Minister, she told Mr Johnson that the Treasury should fund devolved government support schemes “in the event more interventionist measures are required to respond to the public health situation”.

They also called for a four nations Cobra meeting to be convened and for all international arrivals to self-isolate for eight days and take two PCR tests to check whether they have the new variant.

However, this was rejected by Downing Street, which said the plan for arrivals from 4am on Tuesday to take a PCR test by the end of their second day was “the proportionate one to the evidence that we currently have available about this variant”.

The six cases are self-isolating but not in hospital. Contact tracing was continuing to try to establish how they caught the variant and find others to whom they may have transmitted it.

Ms Sturgeon said there was no evidence of any link to the recent Cop26 summit in Glasgow, or the Scotland rugby team’s match at Murrayfield earlier this month with South Africa, the country in which the variant originated.

All close contacts of suspected omicron cases will be advised to self-isolate for 10 days, regardless of whether they have had both jabs. Early indications are that the variant is more transmissible and more resistant to vaccines than the delta variant.