The shops offered extra protection that could be refunded if it was not used within five years.
However, the chain of stores were sold on to new owners that went out of business.
Although ScottishPower settled the claims for £6 million a decade ago, liquidators have said new evidence could lead to further payouts.
MPs yesterday discussed the case with Consumer Affairs Minister Jo Swinson and gave her a dossier of documents on the case, including critical reports by liquidators.
Labour MP Gerry Sutcliffe described the outcome as positive and added: "My colleagues and I welcome the fact that the department is treating this issue with the seriousness it warrants. The commitment to get to the truth of the matter is a significant step towards getting our constituents' money back."