Banks suffered losses on the FTSE 100 this morning after the UK's new markets watchdog announced plans to launch an 18-month investigation into services for small business customers and personal current accounts.
Royal Bank of Scotland was the worst hit, with shares down 1.4% to 317p when markets opened this morning. By mid morning they had fallen to 315p, down 2.6%.
Lloyds shares dropped 0.9% to 72.14p when markets opened, although climbed up to 72.87 by mid-morning, down 0.4%.
Barclays started the day down 0.7% to 207.8p, climbing to 209p by mid-morning, down 0.4%.
The Competition and Markets Authority (CMA) said current account services and SME lending 'lack effective competition', as new and smaller banks still find it hard to challenge the biggest lenders.
The regulator said the 'top' four banks - RBS, Barclays, Lloyds and HSBC - provide more than three-quarters of UK current accounts.
It added that only 3% of consumers switch banks each year and only 4% of SMEs swap their lender.
The watchdog, set up in April, recommends a full-scale inquiry to open up the banking sector, which will start with a consultation and a final decision on a review will be taken in the autumn.