The Accounts Commission report states the extent of the fraud, carried out by IT worker Mark Conway between August 2009 and May 2016, could have been limited if the local authority had addressed significant weaknesses in its invoicing systems.
Conway, who was 52 when he was jailed for more than five years in August last year, had unrestricted access to several systems which allowed him to submit fake invoices to the council with the names of genuine suppliers but giving his own bank account details for payment.
The fraud totalled £1,065,085 resulting from 57 transactions to two bank accounts, with payments ranging from £6,000 to more than £27,000.
The scheme was discovered in May 2016 when, as part of year-end procedures, an invoice for £7,337 was highlighted where supporting information could not be found. Finance staff notified senior management and police were then called in.
The report states: “In particular, the lack of segregation of duties allowed the perpetrator access to a number of systems, enabling them to carry out the fraud.
“Internal controls such as system reconciliations were not carried out or were ineffective, and as a result the payments were not identified as anomalies for further investigation at an early stage.”
The report said the council has since addressed the issues.