The Post Office has admitted there are defects in its Horizon computer system following an independent review.

The review, conducted by independent investigators Second Sight, found two specific occasions over the past two years where defects were identified by the Post Office which had resulted in a shortfall of up to £9,000 at 76 branches. In these instances, the subpostmasters were not held liable and the Post Office rectified these losses.

Over 100 subpostmasters, represented by the Justice for Subpostmasters Alliance (JFSA), had called for the review after being held responsible for financial discrepancies of up to £36,000 that they believe had been caused by the Horizon system. Some subpostmasters affected by the issue are still paying money to the Post Office while others received custodial sentences.

The Second Sight report also said the Post Office’s initial investigation into the issue failed to address the root cause of the problems and that the Post Office should have given more help to affected subpostmasters.

Post Office chief executive Paula Vennells said that although the report showed that “Horizon and its supporting processes function effectively across the network”, there was more work to be done on the system.

“The report does however raise questions about the training and support we have offered to some sub-postmasters and we are determined to address these issues,” she said. “The people who work in the Post Office network in communities across the country are the lifeblood of our business and we take our responsibilities to them very seriously.

“We therefore regret very much if any subpostmaster feels that our standards of support or training have not met their needs, and we are grateful to James Arbuthnot MP and the Justice for Sub-postmasters Alliance (JFSA) for raising these issues with us.”

The Post Office also put forward three proposals in response to the Second Sight report, including the creation of a working party to complete the review cases raised in the past year, an independent review to determine how a safety net might be set up to adjudicate disputed cases in the future, and a new branch user forum that will provide a way for subpostmasters and others to raise issues and insights around business processes, training and support.