Campaigners have branded a surge in deaths in prisons in England and Wales a “national scandal” as the justice secretary, David Gauke, conceded fresh figures revealing a deterioration in safety behind bars was “disturbing”.Prisoner-on-prisoner assaults and self-harm incidents hit record levels, according to the latest batch of statistics from the Ministry of Justice, while deaths in prison jumped 10% to 325.The MoJ has been trying to bring prisons under control with measures such as handing out pepper spray to staff, rolling out in-cell telephones and investing £70m in safety and security across the estate.