LONDON, (Reuters) – A former British senior advisor to Boris Johnson claimed Monday that he would “swear under oath” that Johnson knew the prime minister was holding a party at his home during a COVID-19 lockdown. He also accused Johnson of lying to Parliament.

British media reported at least eleven gatherings at 10 Downing Street, the official residence of the prime minister and his office. Other government departments were also involved between May 2020 to April 2021 when COVID-19 regulations limited social interaction. The facts are being investigated internally.

Johnson last week apologized to parliament for participating in a “bring you own alcohol” event at Downing Street Garden on May 20, 2020. He said it was an office function.

Dominic Cummings is the architect of Britain’s exit from the European Union. He was also a senior advisor to Johnson. In November 2020, he resigned as government minister.

He stated that “not only I, but also other eyewitnesses at the time would swear under penalty of law this is what actually happened,” on his blog.

The week before ITV (LON.) News received an email invitation by Martin Reynolds, Johnson’s Principal Private Secretary to attend a May 20, 2020 event. Reynolds asked that attendees “bring their own alcohol”.

Cummings claimed that Reynolds received a cancellation notice from at least two individuals. Reynolds checked with Johnson and decided if they wanted to continue the invitation.

Cummings wrote in his blog, “The PM agreed that it should,”

Johnson’s spokesperson denied Monday earlier that Johnson was made aware by the Prime Minister of the May 20th event.

According to the spokesperson, “It is not true to state that the prime Minister was warned before that.”