Boris Johnson allegedly attended a birthday party organised for him by his wife Carrie during the first lockdown.
ITV News reported that the Prime Minister was at the indoor event at No10 with 30 people.
At the time of the party on 19 June 2020, social gatherings indoors were still forbidden under the governments own coronavirus rules.
Downing Street said Mr Johnson was only there for 10 minutes.
It also denied a second lockdown-busting gathering was held later in the day.
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