Boris Johnson is continuing to back his senior adviser Dominic Cummings, saying an investigation into whether he broke lockdown rules would not be a "good use" of time.
The prime minister also said the UK was "coming down from level four to level three" on the government's coronavirus alert system and he hopes to make a further announcement this week.
He is being grilled by a senior group of politicians known as the liaison committee – the first time he has faced them since he became leader – amid a growing Tory revolt and plummeting poll ratings over the Dominic Cummings row.
Asked why he had not ordered an investigation into Mr Cummings's actions, Mr Johnson replied: "I'm not certain, right now, that an inquiry into that matter is a very good use of official time.
"We're working flat out on coronavirus."
Mr Johnson was also asked by committee chairman Sir Bernard Jenkin whether the government's "moral authority" had been undermined by the row.
He replied: "This has really been going on for several days now – in the media at least.
More from Boris Johnson
"I, of course, am deeply sorry for all the hurt and pain and anxiety that people have been going through throughout this period – this country has been going through a frankly most difficult time.
"We are asking people to do quite exceptionally tough things, separating them from their families."
The prime minister insisted he would not be adding to his previous comments on Mr Cummings and said the public wanted politicians to focus on "uniting our message" and "focusing on their needs".
Mr Johnson has stood by his top adviser after he was widely criticised for travelling hundreds of miles from London to Durham during the lockdown.
Mr Cummings has said it was necessary in order to seek childcare help and insists he did not break the rules.
One government minister has already quit in protest and the housing secretary admitted "many people across the country" are also aggrieved.
Mr Johnson told the parliamentary committee on Wednesday that it was time for Britain to move on from the controversy.
He said: "It's been a very, very frustrating episode and I understand why people have been so concerned, because this country is going through a horrendously difficult time.
"I totally understand public indignation, I totally understand that, but I do think that… it would be much better if we could now move on and focus on the next steps."
Communities Secretary Robert Jenrick told Sky News earlier that "many people across the country, including many of my colleagues in parliament, believe he made the wrong decisions".