The Competition and Markets Authority (CMA) is to investigate the Experian merger with ClearScore, which would bring together the two largest credit checking firms in the UK.

The two companies first disclosed plans for the £275m acquisition in March. Last month, the CMA told Experian it would mark the deal for investigation unless the company offered “acceptable ways” to address the authority’s competition concerns.

Experian eventually decided not to offer proposals to address the CMA’s concerns and the merger will now be referred for an in-depth investigation by an independent group of CMA panel members. The deadline for the final decision is 14 January 2019.

Explaining its decision, the CMA said: “[The] initial investigation identified concerns that the Experian merger with ClearScore company would be less likely to innovate to help people better understand their finances, potentially leading to people paying more for credit cards and loans.”

At the time of the deal in March, Brian Cassin, chief executive officer of Experian, said: “In acquiring ClearScore, we will take another important step in our strategy to extend the services we provide to UK consumers.

“Our goal is to provide more choice and greater convenience to individuals who want access to personal financial products at the best prices, while also making it easier for credit providers to offer better, more tailored offers to consumers.”

Q4 2017 results for Experian were flat. A 5% growth in revenues for B2B was offset by a 15% fall in consumer services. Credit reporting results were subpar compared to global group results, which reported 8% growth in B2B and a more moderate 5% fall across consumer services.

ClearScore said it was on track to achieve $55m (£42m) in revenues for 2018, up 50% from the previous year.

In what has shaped up to be a tumultuous year for credit firms, in April 2018 Callcredit was acquired by TransUnion in a $1.4bn (£1bn) deal.