He demanded stricter quarantining and testing regimes to reduce the spread of Covid-19 in the UK.
Mr Khan said powers relating to quarantine rules lie with the Government, rather than the Mayor’s Office, and that his calls have so far “fallen on deaf ears”.
In an interview with the PA news agency, the London Mayor also criticised the Government for failing to be clear with its messaging on what people need to do – and insisted that police are enforcing the rules.
He said a “full national lockdown” akin to the one in March is needed because hospitals are now “as busy – if not busier – than they were in March, April and May”, despite the restrictions being “less onerous”.
On international travel, he said: “Other countries that have been affected have not allowed people to come in unless they properly quarantine for a period of time and there is proper testing.
“If you compare and contrast what happens at our airports in relation to the airports in, for example, Seoul, there is a big difference.
“So I’m really frustrated, as the mayor of a city with a number of airports serving us – Heathrow, Gatwick, Stansted, City, plus the Eurostar – at the ease with which people can come in to our city, potentially with new strains of the virus.
“And that’s what we’ve been calling on the Government to make sure they stop the virus coming in through other means, and that’s why it is really important for them also to get a grip with international travel in relation to this virus.”
He added: “I’m asking for much more strict controls in relation to those arriving in our country, including not least far more testing at the point of arrival and proper quarantining before they leave the airport firstly for the testing and before they can leave their homes.”
Matt Hancock says he is ‘incredibly worried’ about the South Africa variant
It comes after former health secretary Jeremy Hunt called for immediate action to close schools, shut borders and ban household mixing, saying the situation was “off-the-scale worse” than previous winter crises faced by the NHS.
“In the face of exponential growth even waiting an extra day causes many avoidable deaths so these plans must now be urgently accelerated,” he said.
Senior Tory Neil O’Brien also said procedures “need to toughen up at the border” in order to prevent cases being imported – a particular concern given the potential for new variants such as the one in South Africa.
The Prime Minister is set to make a televised address this evening, setting out new emergency measures to control the spread of coronavirus in England.
A No 10 spokesman said that the move was in response to the “rapidly escalating” numbers of infections following the emergence of the new variant.
The statement, to be made at 8pm on Monday, will be followed by the recall of Parliament on Wednesday so MPs can debate the measures.
A No 10 spokesman said: “The spread of the new variant of Covid-19 has led to rapidly escalating case numbers across the country.
“The Prime Minister is clear that further steps must now be taken to arrest this rise and to protect the NHS and save lives.”
Additional reporting by PA Media.