John Browne stepped down as chief executive officer of BP Plc three months earlier than planned after losing a legal battle to prevent the publication of claims he let a former boyfriend use company resources. BP, Europe’s second-biggest oil company, said yesterday in London that Tony Hayward, who was scheduled to replace Lord Browne August 1, takes over the position immediately. BP said allegations Lord Browne misused resources were “unfounded or insubstantive.” Lord Browne’s decision follows a court ruling that he lied in his bid to block publication by the Mail of the boyfriend’s account of their four-year relationship.