LONDON, Jan 18 (Reuters) - British finance minister Rishi Sunak said he believed Prime Minister Boris Johnson"s explanation over a drinks party in the gardens of Downing Street. Johnson last week apologised to parliament for attending a "bring your own booze" gathering in the Downing Street garden on May 20, 2020. He said he had thought it was a work event and that he attended for 25 minutes to thank staff. Asked if he believed Johnson"s account to parliament, Sunak told reporters: "Of course I do - the Prime Minister set out his understanding of this matter in Parliament last week." Dominic Cummings, Johnson"s aide at the time of the event, said he told Johnson about the party in advance. The prime minister"s office have said it is not true he was told in advance. read more Asked whether Johnson would have to resign if it was proven he had lied to parliament, Sunak said: "I"m not going to get into hypotheticals. The ministerial code is clear on these matters. "But as you know, Sue Gray is conducting an inquiry into the situation. I think it"s right that we allow her to conclude that job." (This story corrects spelling of Gray in final paragraph)