Watch as Partygate investigator Sue Gray gave evidence to the Covid inquiry in Belfast on Thursday, 16 May.
The former senior civil servant, now Sir Keir Starmer's chief of staff, authored a report looking into Boris Johnson over lockdown breaches in Downing Street during the pandemic.
It was launched after media reports of gatherings in the locale of the British prime minister.
Ms Gray concluded there were "failures of leadership and judgment in No 10 and the Cabinet Office" for which "the senior leadership at the centre, both political and official, must bear responsibility".
“The events that I investigated were attended by leaders in government. Many of these events should not have been allowed to happen,” she added.
Ms Gray found that leaving dos and other boozy gatherings, including drinking until the early hours of the morning, were held while restrictions were in place.
The findings were widely viewed as hastening Mr Johnson’s departure from the top job.
The Metropolitan Police conducted a probe, named Operation Hillman, into rule breaches in Downing Street and Whitehall.
Officers said a total of 126 fines were issued to 83 people in the scandal.
Mr Johnson, his wife Carrie, and Rishi Sunak all received fixed penalty notices for attending a birthday gathering for the then-PM in No 10.
After writing the report, Ms Gray joined the Labour leader's team,
A government investigation found she breached the civil service code by talking to Sir Keir about a job four months before leaving Whitehall.
A Labour spokesperson said the finding by the Cabinet Office was “Mickey Mouse nonsense” and a “political stunt” by the Tories, adding: “All rules were complied with."
Ms Gray began working as Labour leader’s chief of staff after a six-month cooling off period from when she quit as a senior civil servant in March 2023.
