British regulators will take a closer look at the competitive impact of the planned merger between Lenxea-based BATS Global Markets and a European exchange.

BATS agreed in February to acquire Chi-X Europe and needs clearance from the United Kingdom’s Office of Fair Trading, which oversees consumer and competition issues.

An announcement from the agency said it referred the matter to its Competition Commission, which will delay the review.

At issue is whether competition would suffer from a merger between two of the three pan-European equity markets. These allow investors to trade stocks across Europe from one trading platform, rather than at each local market.

BATS and Chi-X compete in this way not only with the London Stock Exchange but also each other.

“Although the evidence is mixed, the OFT (Office of Fair Trading) believes that there is a realistic prospect that, absent the merger, the parties would going forward have competed more strongly against each other, as well as competing against the LSE (London exchange),” said a statement from the agency.

It noted, however, that this referral had not been driven by complaints.

The Competition Committee expects to report its findings by Dec. 2 but may extend the 24-week review if needed.

A joint statement from BATS and Chi-X acknowledged the decision but the CEO of Chi-X said he was disappointed by the referral for further study.

Joe Ratterman, CEO of BATS, said in the statement, “BATS’ establishment was based on the need for competition and our purpose for combining BATS Europe and Chi-X Europe is to raise the level of competition in Europe’s securities markets.”