The level of competition in investment and corporate banking services are to be investigated by the UK's financial regulator, the Financial Conduct Authority (FCA).
Launching its first review of the sector, the FCA said that the potential benefits of improvements could be high. It said there was "limited clarity over price and quality of services". And it said that could make it difficult for clients to assess whether they were "getting value for money".
"We have chosen this particular area because the benefits of effective competition in the market could be significant," said Christopher Woolard, director of strategy and competition at the FCA.
"The UK is a global hub for investment banking, and this sector plays a crucial role in our economy, helping companies raise capital for investment, expansion and funding ongoing operations."
The FCA also said that following discussions with stakeholders and firms, there were "unanswered questions about potential conflicts of interest and value for money in this market".
It said feedback received so far included concerns around transparency, conflicts of interest, and the impact that bundling services together has on competition - including new firms' ability to enter the market.
Terms of reference for the investigation will be published in spring.
In response to the FCA's announcement, the British Bankers' Association said: "Banks compete vigorously for new clients every day and we believe that the market in London is one of the most competitive in the world.
"All banks will co-operate fully with this investigation, but we would urge the regulator to take into account the considerable and fast-moving changes that are currently taking place in wholesale markets."
The Institute of Directors (IoD), a business lobby group, welcomed the report but said that it thought the FCA should prioritise looking at the fund management industry.
"Greater clarity is required about their pay, fees, tradition activating and perhaps most pertinent, their commitment to stewardship and their voting record," said Oliver Parry, senior corporate governance adviser at the IoD.