Britain's beleaguered Health Secretary Matt Hancock on Friday conceded he had "let people down" after revelations he was having an affair with a close aide who he appointed in secret last year.

Opposition parties demanded Hancock's resignation, after The Sun newspaper published a security camera still obtained from a whistleblower showing him kissing the aide in his office on May 6, in violation of rules on social distancing.

"I accept that I breached the social distancing guidance in these circumstances. I have let people down and am very sorry," Hancock said in a statement, while insisting he would stay on.

"I remain focused on working to get the country out of this pandemic, and would be grateful for privacy for my family on this personal matter," he said.

The main opposition Labour party also said the government needed to answer questions about the undisclosed appointment of Gina Coladangelo, a former lobbyist, to Hancock's top advisory team. Both she and Hancock are married.

There was no immediate response from Downing Street. 

But Transport Secretary Grant Shapps said Coladangelo would have gone through an "incredibly rigorous" process to get the job.

"There are no shortcuts to that, as anyone who has had anything to do with the appointments system in the civil service knows," he told Sky News.

Shapps declined to comment further on what he said was an "entirely personal" matter for his cabinet colleague.

Last week, Hancock rejected criticism of his handling of the Covid pandemic after private WhatsApp exchanges emerged in which Prime Minister Boris Johnson appeared to describe him as "hopeless".

Hancock has also previously faced allegations that he lied to Johnson and awarded a contract to an unqualified friend.

He has faced further questions about his ownership of shares in a family company that won a Covid-related contract from his ministry last year.

In May 2020, scientist Neil Ferguson resigned from a government advisory panel after breaking rules on social distancing, following media reports that he had allowed a woman said to be his "lover" to visit him at home.

But when Johnson's then-chief adviser Dominic Cummings broke strict lockdown rules to travel across the country last year, causing a public uproar, the prime minister refused to sack him.