The proposed merger between mobile telephone companies Three and O2 looks in danger, as The Competition and Markets Authority (CMA) has said that it has “serious doubts” about deal.

The CMA said that the merger was likely to cause “long-term damage” to the UK telecoms market as it would leave the total number of mobile operators in the country at just three. The European Commission has until May 19th to make a decision on the proposed £10.5 billion tie-up.