The disciplinary process in the National Offender Management Service (NOMS), including authority for suspending staff from duty, is devolved to a local level.
Public sector Prison Service establishments have only been required to notify headquarters of their intention to suspend a member of staff from duty since October 2007. According to the records held centrally, on 28 October 2009 a total of 48 members of staff were suspended from duty while some aspect of their conduct was under investigation. While the reasons for suspension are recorded centrally, this would be under a broad heading and not to the level of detail required to answer your specific question.
In order to provide a detailed response to the hon. and learned Member’s question, NOMS would need to contact all public sector Prison Service establishments, ask them to provide details of all staff suspensions for the last three years and update the central records accordingly. To retrieve these data would incur disproportionate cost.