Regulators have warned that Britain’s challenger banks online must do more to stop criminals abusing their platforms.

Friday, the Financial Conduct Authority published the findings of a review into financial crime controls at several U.K. challenger banks — younger banks set up with the aim of taking on incumbent lenders.

Although the FCA did not name any companies, it said that its review was focused on six banks which are digital challengers. Half of these banks were digital. The watchdog stated that these six banks collectively had more than 8,000,000 customers. Revolut, Wise and other payment service providers were not included in the review.

According to the regulator, it discovered weaknesses in banks that were challenging customers’ due diligence. Some firms failed to properly assess financial crime risk when boarding clients. The regulator said that challenger banks didn’t have adequate customer risk assessments, in certain cases.

Sarah Pritchard (executive director markets, FCA) stated in a Friday statement that “challenger banks are an integral part of the UK’s retail banking offer.”

There cannot be an acceptable compromise between fast and easy account opening and financial crime prevention. This review is a reminder to challenger banks that they must consider these findings and work on improving their financial crime control systems in order to avoid harm.

There are many Fintech companies. under pressure to improve their financial crime controlsThis is especially true in light of the economic sanctions placed on Russia following its unprovoked invasion Ukraine.

Many upstart lenders, including Starling and Monzo have been able to thrive because of the U.K.’s fintech-friendly laws. Regulators are becoming more concerned that these upstart lenders may not have as strict controls as established banks. Their platforms were designed to speed up the process of applying for loans or accounts.

According to the FCA, it is expecting challenger banks’ financial crimes defenses to evolve to match their user growth. It also expects them to adjust their due diligence procedures to address the higher risk of sanctions fraud.

Monzo, a popular mobile-based bank that uses apps to make money, disclosed last year that the FCA was conducting an investigation into possible breaches of antimoney laundering laws. The company stated at the time that the investigation is still “in an early stage” and that they are cooperating with authorities.