By Ian Walker

LONDON--The U.K. Competition and Markets Authority Thursday announced an "in-depth" market investigation into the personal current account and SME [small to medium enterprise] retail banking sectors, confirming its provisional decision in July.

"Having carefully considered the consultation responses, the CMA continues to have concerns about the effectiveness of competition in these sectors and has decided to make a market investigation reference," it said.

A number of issues are under consideration, including the low levels of customers shopping around and switching; limited transparency, and difficulties for customers in making comparisons between banks, particularly for complex overdraft charges on personal current accounts.

The regulator will also investigate the continuing barriers to entry and expansion into the sector, limiting the ability of smaller and newer providers to develop their businesses.

Alongside this, the CMA said it will review the competition undertakings put in place in 2002 into small and medium-sized enterprise banking, to examine whether any change of circumstances since then warrant their being varied or terminated.

-Write to Ian Walker at ian.walker@wsj.com; @IanWalk40289749

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