The Financial Conduct Authority is to launch a probe into how wealth managers use in-house funds.
The news was revealed in the financial watchdog's annual review, with the regulator concerned that there may be conflicts of interest at work.
'We will assess how wealth managers and private banks effectively control the conflicts of interest that arise when client assets are invested in in-house investments,' the FCA said.
The business review also revealed the FCA's funding requirement would rise by £6.3 million to £452 million.
The news increases the pressure on wealth firms after the regulator launched an investigation into suitability in 2011.
This included a letter to the chief executives of a number of wealth firms asking for evidence they were meeting suitability requirements.
Last week the FCA showed it had not lost focus of the issue when it hit Santander with a £12.4 million fine after finding several failings in its investment advice process.
The FCA is also believed to have made increasing use 'arrow' (unannounced and targeted) visits on wealth managers where files dating back a decade are analysed.