Dr Hilary Jones criticises people talking about holidays at the moment as "it's not appropriate".
The Good Morning Britain doctor was on discussing a year since the first lockdown was announced in the UK with hosts Susanna Reid and Ben Shephard.
The comment came after a ban on anyone leaving the UK without a reasonable excuse has been announced as part of new coronavirus laws coming into force next week.
Fines of up to £5,000 could be dished out to those attempting to leave the country without a reasonable excuse.
It also comes amid concerns about a possible third wave in Europe as cases rates rise.
Speaking on Tuesday's GMB, Susanna said stated to Dr Hilary: "What happens in Europe will happen to us."
To which he continued: "People talking about holidays at the moment, it’s not appropriate. It’s foolhardy…
"It’s international travel that's transmitting the virus more quickly than anything else. Aircraft and people being able to move very quickly throughout the world.
"We're also seeing new variants, it's not just the original virus that's causing mayhem, it's the new variants that are also potentially very damaging."
Dr Hilary continued: "Whilst we are doing very well with our vaccination schedule here, the new variants threaten the immunity of the vaccines that we’re currently using. We don't want to go back to the position we were in a year ago.
"If we're too lax with the regulations, we will have another wave, we will have more people in hospital. More deaths again and people will suffer with their mental health, with their education, and that’s why I think it’s really imperative that people take this seriously still and obey the regulations which are set down by the Government but advised through scientists."
The new legislation is set to be approved by MPs on Thursday.
While foreign holidays are not currently permitted under the 'stay at home' rule, the ban on leaving the UK will then become specified law when this message is dropped on Monday, March 29.
