The revelation came to light after representatives from the FOS were quizzed by the Treasury Committee about its backlog of cases.

Nausicaa Delfas, interim chief executive and chief ombudsman at FOS, said that when she took on the role last year some complainants were waiting up to four years for their case to be looked at.

Delfas said the FOS was committed to have no cases more than 18-months-old by the end of this financial year and claimed the service was making ‘significant inroads’ into the backlog of cases.

When Delfas joined the FOS in May 2021, the service had 90,000 unallocated cases – those that had not yet been looked at. This figure has since been halved, with about 43,000 unallocated cases now outstanding, and the oldest cases being dealt with first.

Ms Delfas said: “We’re going to continue on that path, it’s one of our top priorities to get through that backlog so that we can get into a steady state.”

She admitted that if someone took a case to the FOS now it would take about seven months for their case to be resolved – but she was hoping the typical case time would be reduced to four months.

The Financial Ombudsman Service is a free service that settles complaints between consumers and businesses that provide financial services. It can order firms to put things right and compensate customers.

The committee heard the ombudsman service had received many pandemic-related complaints such as those concerning wedding insurance, travel insurance and health insurance. Other cases included high-cost, unaffordable lending and guarantor loans.

Jenny Ross, Which? Money editor, said: “It is shocking that some victims of financially and emotionally devastating crimes like bank transfer fraud have been left in limbo for years. It is vital that the ombudsman makes good on this pledge to clear the backlog of cases quickly and fairly.

“The huge rise in push payment scam complaints suggests victims are still facing a lottery when it comes to getting their money back, highlighting why urgent action is needed to make sure banks treat victims fairly in the first place.

“The government must make good on its commitment to legislate to make reimbursement mandatory in a way that ensures victims get fair and consistent treatment. The regulator must also ensure it is ready to act the moment that legislation is passed.”