Health Secretary Matt Hancock has admitted breaking social distancing rules after pictures of him kissing an aide were published in a newspaper.
He said he had “let people down” after photos emerged of him with Gina Coladangelo – whom he appointed – and was “very sorry”.
Labour urged the PM to sack Mr Hancock, calling his position “untenable”.
But the health secretary said he would stay “focused” on dealing with the pandemic.
The Sun reported that its pictures of Mr Hancock and Ms Coladangelo, both of whom are married with children, had been taken inside the Department of Health in early May.
Labour Party chairwoman Annaliese Dodds said: “If Matt Hancock has been secretly having a relationship with an adviser in his office – whom he personally appointed to a taxpayer-funded role – it is a blatant abuse of power and a clear conflict of interest.
“The charge sheet against Matt Hancock includes wasting taxpayers’ money, leaving care homes exposed and now being accused of breaking his own Covid rules.
“His position is hopelessly untenable. Boris Johnson should sack him.”
A government spokesman said Ms Coladangelo’s appointment had been “made in the usual way” and had “followed correct procedure”.
And, in a statement, Mr Hancock, a 42-year-old father of three, said: “I accept that I breached the social distancing guidance in these circumstances. I have let people down and am very sorry.
“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.”
The health secretary cancelled a visit to a Covid vaccination centre at Newmarket Racecourse, in his West Suffolk constituency, on Friday morning, a few hours after the Sun’s story was published.
‘Hypocrisy’
Ms Coladangelo, who has known the health secretary since they were at Oxford University together, was made a non-executive director of the Department of Health last September.
The role comes with a £15,000 salary and involves 15-to-20 days of work per year.
The Liberal Democrats called on Mr Hancock to resign and accused him of “hypocrisy” over social distancing.
Health spokeswoman Munira Wilson said: “He was telling families not to hug loved ones, while doing whatever he liked in the workplace.”
Mr Hancock’s ministerial colleagues rallied around him, with International Development Secretary Truss told the BBC: “[Mr Hancock] does have my support [in cabinet]. This is a personal matter.”
Transport Secretary Grant Shapps told BBC Radio 4’s Today programme: “I think there has been for a long time a complete difference between what people do in their job… and what they do in their personal lives.”
Ms Coladangelo, 43, is married to Oliver Bonas founder Oliver Tress and Mr Hancock’s wife of 15 years, Martha, is an osteopath.
The government’s guidelines for England on hugging friends who are not part of your household states that people can exercise “personal judgement”, but should remain cautious.
In May last year, epidemiologist Professor Neil Ferguson resigned from the government’s scientific advisory group (SAGE) after it emerged he had broken lockdown rules when a woman he was reportedly in a relationship with visited his home.
Mr Hancock called Prof Ferguson’s actions “extraordinary”, adding that social distancing rules were “there for everyone” and were “deadly serious”.
On Friday, Labour’s First Minister of Wales Mark Drakeford said Mr Hancock had been “quick to condemn” Prof Ferguson, adding: “Certainly here in Wales I always expect the whole of our ministerial team to observe the rules we expect other people to observe.
“We can’t make laws for other people and not be willing to abide by them yourself.”