By Elizabeth Piper and Andrew MacAskill LONDON (Reuters) – Former British Prime Minister John Major accused his fellow Conservative Boris Johnson on Thursday of breaking COVID-19 lockdown laws and said he should resign if he is found to have deliberately misled parliament with his “brazen excuses”. Johnson is facing his gravest crisis since becoming prime minister in 2019 over a steady drip of reports of boozy events in his Downing Street office and residence while Britain was under strict coronavirus restrictions. He has resisted calls, including from some in his governing Conservative Party,…