LONDON (REUTERS) - Britain's competition watchdog launched a full investigation into banking services for small business customers and personal accounts on Thursday that could see big banks forced to sell branches or face other remedial measures.

The Competition and Markets Authority said banks have not done enough to meet the needs of retail customers or small and medium-sized businesses, such as making it easier to switch banks or providing clear information on fees.

The investigation, which could take about 18 months, had been expected after the CMA said in July a full investigation was on the cards.