The Financial Conduct Authority (FCA) is to investigate about 30 million insurance company policies over concerns that customers are subject to "unfair" conditions.
The investigation will include pensions, endowments, investment bonds and life insurance policies sold in the UK between the 1970s and 2000, the BBC reports.
The FCA will look into policies which penalise savers who want to switch providers.
The regulator told the Daily Telegraph it might "intervene on exit charges".
A large number of policies sold to consumers in the 30 years leading to the millennium include terms which penalise those attempting to switch to a cheaper provider.
Some savers face losing up to half of their savings if they move to another company.
The FCA also said it feared "zombie" funds, which are closed to new clients, are being used by insurers to pay bills from other parts of their businesses.
Details of the investigation will be published on Monday, as part of the FCA's annual business plan.
Clive Adamson, the FCA's director of supervision, told the Daily Telegraph: "We want to find out how closed-book products are being serviced by insurance companies, as we are concerned insurers are allocating an unfair amount of overheads to historic funds.
"As firms cut prices and create new products, there is a danger that customers with older contracts are forgotten," Mr Adamson added.
"We want to ensure they get a fair deal."
