BCS, The Chartered Institute for IT has urged the government to urgently review an existing law that assumes the reliability of computers.

The organisation has criticised the legal presumption that computer systems are always correct because it means that there is no burden on the prosecution to prove their reliability.

It was under this law that sub-postmasters were prosecuted by the Post Office after being accused of stealing from the company.

From 2000, the Post Office brought charges against over 700 staff based on data from its flawed Horizon IT system.

Some of these staff members went to prison following convictions for theft, false accounting and fraud.

“The Post Office could rely on the common law position that the courts were entitled to assume that the IT system was operating correctly," said Dr Sam De Silva, chair of BCS law specialist group and technology partner at international law firm CMA. "Without the benefit of the advice of IT experts supporting them, it was for the Post Office staff to prove that the outputs and logs from the computer system were flawed or not accurate.

"Yet how could non-IT specialists be expected to prove this when even some experienced IT professionals would find it a challenge to do so?"

De Silva said that if the Post Office had been required to prove that its computer system was operating reliably, most of the individual cases against the Post Office staff may have had a different outcome.

The comments come as an inquiry into the scandal sees those involved facing questions from MPs this week.

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