Dr Hilary Jones has issued a stark warning on the new South African coronavirus variant which has spread to eight areas of the UK.
He told Good Morning Britain's Piers Morgan, Susanna Reid and Charlotte Hawkins that it is of "great concern", Berkshire Live reports.
It comes as 80,000 people living in the eight affected areas of the UK are being tested door-to-door for the new variant as 11 cases with no links to South Africa emerged.
Dr Hilary told viewers: "Because it is more transmissible, it will spread more readily, and there are fears it could be a third more resistant to current vaccinations - so that is a great concern.
"And that's why 80,000 people are being asked to come forward and accept PCR tests to find out if it is more prevalent in those areas."
He said it was too late to bottle this one up with the closing of borders as it would do "very little to stop the strain from spreading further."
There would "inevitably" be more variants of the Covid-19 virus in the future, he explained.
"The only way to prevent more variants coming in is to quarantine everybody, in mandatory fashion, self-isolate them, test them, don't release them until they test negative on more than one occasion."
He said unless the quarantine is mandatory and under surveillance in hotels, people don't quarantine.
"There are 21,000 people coming through our airports every day, they are not being quarantined, they are not being quarantined and they may have the South African variant", he added, and said they may also have other variants.
Good Morning Britain on ITV airs from 6am Monday to Friday.
