UK Chancellor Rishi Sunak has offered an unreserved apology and paid the fine imposed on him by Scotland Yard for breaching COVID lockdown rules in June 2020, when he attended a birthday party at Downing Street for his boss Prime Minister Boris Johnson.

The Indian-origin finance minister offered the apology in a statement issued on Tuesday evening, after Johnson's own apology and confirmation that he too had paid up his fine.

The so-called partygate scandal, of around 12 parties being held at Downing Street and other UK government offices in Whitehall in breach of coronavirus legislation in place during 2020-2021, has been under police investigation as part of Operation Hillman.

I can confirm I have received a fixed penalty notice from the Metropolitan Police with regards to a gathering held on June 19 in Downing Street, Sunak said in his statement. I offer an unreserved apology," the 41-year-old minister said.

"I understand that for figures in public office, the rules must be applied stringently in order to maintain public confidence. I respect the decision that has been made and have paid the fine. I respect the decision that has been made and have paid the fine," he said.

The partygate saga comes at the end of a particularly tough few days for Sunak's role as Chancellor, after he faced allegations of allegedly improper tax savings by his Indian wife Akshata Murty and his own US Green Card status while in a high political office in Britain.

Murty, the daughter of Infosys co-founder Narayana Murthy, has since issued a statement to say she will now choose to pay all her taxes in the UK to avoid her legally permitted non-domicile tax status becoming a distraction for her minister husband.

Sunak, meanwhile, has referred himself to the government's independent watchdog to confirm that he made all the legally required ministerial declarations of his financial affairs.

While the Opposition has demanded the resignation of the two senior-most government officials for breaking the law with partygate, both Johnson and Sunak have insisted that they intend to get on with their jobs. Like the Prime Minister, I am focussed on delivering for the British people at this challenging time, said Sunak.

The UK Cabinet ministers and Conservative MPs have largely rallied around the duo, as a leadership contest is not seen as ideal in the midst of the Russia-Ukraine conflict and the severe cost of living crisis domestically. Earlier on Tuesday, in a video statement from his Chequers residence, Johnson said: "In all frankness, at that time it did not occur to me that this might have been a breach of the rules. But, of course, the police have found otherwise and I fully respect the outcome of their investigation."

His wife, Carrie Johnson, also apologised unreservedly after confirming that she had received and paid up a fine for the same Cabinet Room party at Downing Street, to which she had brought a cake to surprise her husband on his birthday on June 19, 2020.

It has led to Johnson becoming the first UK Prime Minister to be sanctioned for breaking the law. It is expected that the Johnsons and Sunak would have most likely been handed a 200 pounds fixed penalty notice each, which is a sanction similar to a parking ticket. Unless it is challenged, there is no court process involved after the fine imposed is paid up.

Reports of parties being held at Downing Street during the coronavirus lockdowns that limited such gatherings to control the spread of the deadly virus first emerged in December 2021. Both Johnson and Sunak had said at the time that they did not attend any parties. However, as revelations of several gatherings emerged, the UK prime minister ordered an inquiry into the allegations of rule-breaking, led by senior civil servant Sue Gray, and was also forced to apologise in Parliament over the reports of lockdown breaches.

Gray passed on information to the Met Police at the end of her inquiry, which found some wrongdoing, and Operation Hillman was launched earlier this year.

The complete Sue Gray report will not be released until the Met Police have concluded their investigation, which is when Johnson is also committed to make a statement to the House of Commons.