The pop star, best known for her hits "Hot Right Now" and "Your Song," said in an Instagram story she had gone to "a small gathering with some friends" to celebrate her birthday.
"This was a serious and inexcusable error of judgement," Ora said. "Given the restrictions, I realise how irresponsible these actions were and I take full responsibility."
England is currently in lockdown to stop the spread of COVID-19, prohibiting people from different households from mixing indoors, unless they are part of the same household or support bubble. Pubs and restaurants have also been closed except for take-aways.
The lockdown is set to end on Dec. 2, but much of the country is set to remain under tough restrictions as the British government tries to curb the spread of the virus ahead of the winter holidays.
"It was a spur of the moment decision made with the misguided view that we were coming out of lockdown and this would be OK," Ora said. "I'm deeply sorry for breaking the rules and in turn understand that this puts people at risk."
British media reported that the party, which included more than 30 people, took place at a high-end restaurant in west London's swanky Notting Hill neighborhood. NBC News was not able to reach the restaurant for comment.
London's Metropolitan Police said officers had been called to reports of breach of lockdown rules, but had not found any offense being committed, Reuters reported.
“Officers continue to assess the allegations and are liaising with the local authority regarding a potential breach of regulations at the premises,” police said in a statement.
A local council where the restaurant is located told NBC News that it was aware of the reports of Ora's party and will be conducting an investigation.
The BBC reported that Ora will pay a fine of unconfirmed amount to the police.
The U.K. has been hit hard by the coronavirus, with 58,448 COVID-19 deaths since the pandemic started, the highest death toll in Europe. The virus has also wreaked havoc on the country’s economy as Britain’s public debt has ballooned to more than 2 trillion pounds during the pandemic.
This article was originally published on NBCNews.com.