The Office of Fair Trading (OFT) has announced a probe into parts of the investment banking industry.
The investigation will focus on the prices which investment banks charge for services such as advising companies and underwriting share offers.
The study will examine whether parts of the work done by investment banks may affect competition or consumers.
The probe will look at rights issues and other types of equity-raising by the 350 largest UK public companies.
Firms whose UK business includes an investment banking arm include Royal Bank of Scotland, Barclays, Goldman Sachs, Morgan Stanley and Citigroup.
The OFT said it would study the efficiency of the equity underwriting market and identify any areas for improvement.
The investigation will start in the summer.
"In 2009, companies raised an estimated £70bn of equity capital in the UK, paying an estimated £2bn in fees for equity underwriting and associated services," the OFT said.
"Initial discussions have confirmed that there is some dissatisfaction with these services among corporate users of the market."
The watchdog said it would assess how underwriting and related services were provided and purchased, and would also look at how the regulatory environment affected the provision of these services.