The U.K. Competition and Markets Authority is examining whether the planned combination of OneSavings Bank PLC and Charter Court Financial Services Group PLC would substantially reduce competition.

The regulator is seeking comments on the transaction until June 19, and will announce its decision whether or not to refer the deal for a phase two investigation July 30.

In March, the challenger banks announced an all-share merger, which would create an entity with roughly £15.6 billion of net customer loans and £13.2 billion of customer deposits. The merger is expected to take effect in the third quarter, subject to certain conditions.