Prof Ferguson, whose advice to the prime minister led to the UK lockdown, said he regretted “undermining” the messages on social distancing.
It follows a Daily Telegraph story that a woman, said to be his “married lover”, visited his home in lockdown.
His modelling of the virus’s transmission suggested 250,000 people could die without drastic action.
This led Prime Minister Boris Johnson to announce on 23 March that he was imposing widespread curbs on daily life aimed at stopping the spread of the virus.
Under those measures, partners who do not live together were no longer allowed to see each other.