Keir Starmer has said he accepted free accommodation from a Labour donor so his son could study for his GCSEs in peace.
The prime minister declared the gift, estimated to be have been worth £20,000 in his register of interests.
It was given to him by Labour peer Lord Alli, the multi-millionaire who also bought Starmer £20,000-worth of suits and glasses, as well as £5,000 in dresses for his wife.
Asked by Today programme presenter Nick Robinson why he needed free accommodation during the general election campaign, the PM said: “My boy, 16, was in the middle of his GCSEs.
“I made him a promise, a promise that he would be able to get to his school, do his exams, without being disturbed.
“We have lots of journalists outside our house where we live and I’m not complaining about that, that’s fine.
“But if you’re a 16-year-old trying to do your GCSEs and it’s your one chance in life – I promised him we would move somewhere, get out of the house and go somewhere where he could be peacefully studying.
“Somebody then offered me accommodation where we could do that. I took that up and it was the right thing to do.”
Starmer has also come under fire for taking hospitality at Arsenal FC, the team he goes to watch with his son.
He has said he was told the pair could not sit in their usual seats among the fans now that he is prime minister because of security fears.
Following reports that he would now be sitting in a corporate box at the Emirates Stadium, the PM said that was not the case.
He told LBC: “The club said, ‘well, why don’t you be our guests in the directors’ box?’. Now, people say, ‘well, why don’t you pay for that?’ You can’t pay for a ticket in the directors’ box.”