Around 10,500 customers had complaints open with the Financial Ombudsman Service (FOS) at the time the payday lender collapsed in August 2018.

But these customers were told the ombudsman will not deal with their complaints and they won’t get compensation because high cost short-term credit firms are not covered by the Financial Services Compensation Scheme (FSCS).

Treasury Committee chair Nicky Morgan wrote to the city regulator – the Financial Conduct Authority (FCA) – expressing concerns that customers, many of whom are likely to be vulnerable, may be at a significant financial disadvantage.

In response, Andrew Bailey, chief executive of the FCA, said customers who had complaints open with the ombudsman should contact Grant Thornton, Wonga’s administrators.

Morgan has written to Grant Thornton asking how it plans to deal with the complaints.

Morgan said: “It cannot be right that over 10,000 people who may have been mis-sold loans are just cast aside, especially as many will be vulnerable consumers.

“These people have been left to fend for themselves by Wonga, the FCA and the FOS. They’ve been allowed to fall through the cracks, with nobody taking responsibility for their mistreatment.

“I have written to Grant Thornton, Wonga’s administrators, to understand how they intend to progress outstanding complaints against Wonga.

“If Wonga continues to damage people’s finances from beyond the grave, it may be time for the government to intervene.”

Wonga, which was the UK’s biggest payday lender, went into administration following a surge in compensation claims.