The Competition and Markets Authority (CMA) said on Tuesday that it has fast-tracked BT Group's deal to acquire EE to a "phase 2" investigation - a deeper probe of the deal - due to concerns about competition.The CMA said that the sale of EE to BT by Deutsche Telekom and Orange could lead to a substantial lessening of competition in the UK mobile phone market.On 15 May, BT submitted a request for a fast-track reference to a phase 2 investigation as it set out its argument for the deal."The CMA has found that the transaction meets the test for reference in that it gives rise to a realistic prospect of a substantial lessening of competition in relation to the supply of wholesale access and call origination services to mobile virtual network operators and fibre mobile backhaul services to mobile network operators in the UK."Andrea Coscelli, CMA executive director of Markets and Mergers and decision-maker in this case, said: "BT and EE are leading suppliers of UK telecommunications services and together they will have a strong presence in many telecommunications markets.""They also supply important inputs at the wholesale level, which enable other communications providers to compete at the retail level in the provision of mobile services. We have found that there is a real risk that the merger could reduce their incentives to supply these inputs and that this could have a detrimental impact on the retail mobile market."