The boss of the Co-op is stepping down weeks after the BBC reported on claims of a "toxic culture" at the top of the food and services group. A letter sent to Co-op board members had complained of "fear and alienation" among even senior staff who felt scared to raise concerns about the direction of the business in front of the leadership team, claims the Co-op said it didn't recognise at the time. Shirine Khoury-Haq's departure comes as the group reported a £126m annual loss, after its sales took a massive hit from a cyber-attack last year. Khoury-Haq said it had been an honour to lead the organisation and wished it success in the future. She will step down as chief executive on 29 March. Kate Allum, currently a member-nominated director on the Co-op board, has been appointed interim group CEO. Khoury-Haq has been with the Co-op for seven years, including four at the helm. The last year has been a particularly turbulent one for the 180-year-old member-owned group.…