Two damning reviews into serious disclosure failures by the Serious Fraud Office have cost the taxpayer nearly £450,000, the government has revealed.

An independent review into the collapse of the case against two former directors of outsourcing giant Serco – which landed the watchdog with a £2.7m costs bill – cost the SFO nearly £360,000, attorney general Michael Ellis QC said.

Brian Altman QC, a leading criminal barrister who was commissioned to review the Serco case, found that there were ‘systemic problems of real concern’ in relation to the SFO’s disclosure, including that the appointed disclosure officer’s ‘inexperience should have disqualified him from appointment as disclosure officer on such a large and complex case’.

A separate review into the SFO’s conduct of its calamitous Unaoil bribery case has cost nearly £85,000 so far with further costs expected to be incurred, Ellis told Labour MP Andy Slaughter in response to a written question.

Ellis added: ‘There are some costs outstanding, but it is anticipated these will not increase the overall cost of the review significantly. The total costs will be recovered from the SFO.’

Sir David Calvert-Smith – a former High Court judge and ex-director of public prosecutions – criticised ‘fundamental’ failures by the SFO during the Unaoil investigation and prosecution, including poor record-keeping and ‘inadequate resourcing’.

The SFO was also heavily criticised by the Court of Appeal over ‘wholly inappropriate’ contacts between senior officials – including the watchdog’s director Lisa Osofsky – and David Tinsley, a ‘fixer’ who was acting on behalf of the family behind Unaoil.

Three of the four men who were jailed for bribery have now had their convictions quashed by the Court of Appeal and the SFO’s estimated in its annual report that just one of those three cases will lead to a £1.5m costs bill.

The ongoing fallout from the Unaoil case has piled the pressure on Osofsky, who has faced calls to resign as further details of her involvement with Tinsley emerged throughout the appeal process.

However, the under-fire director – whose five-year term ends in August 2023 – told MPs in February that she had not decided whether she will seek to continue in post and this week called for reform of disclosure rules to ‘rebalance the system for victims and justice’.