the post office asked forensic accountants second sight to investigate the horizon it system in 2012 , following complaints from dozens of subpostmasters who said they had been wrongly accused of theft , fraud and false accounting when cash shortfalls were discovered .
the post office failed to properly investigate why money gone missing from branches before launching court proceedings against subpostmasters .
now a leaked copy of the accountants ' independent report has suggested that the discrepancies could have been caused by computer failures .