Downing Street said: “That was a brief error of judgement. The PM removed his seatbelt to film a small clip. He fully accepts this was a mistake and apologises about it.”
Labour said Mr Sunak’s video was adding to “endless painful viewing” after he previously appeared to struggle to make a contactless payment with his card.
“Rishi Sunak doesn’t know how to manage a seatbelt, his debit card, a train service, the economy, this country,” a spokeswoman said.
“This list is growing every day, and it’s making for endless painful viewing.”
Liberal Democrat deputy leader Daisy Cooper said: “It seems like the PM is getting too used to flying around in private jets that he’s forgotten to wear a seatbelt in a car.
“The fact he’s breaking a basic law is just embarrassing and frankly dangerous.”
The AA warned of the dangers of not wearing a seatbelt.
“No matter who you are it is important to wear your seatbelt when in the car,” an AA spokesman said.
“In 2020, a fifth of all car occupant fatalities were not wearing a seatbelt.”