T-Mobile and Orange's proposed merger has come under fire from rival broadband providers, according to reports.
O2, 3 and Vodafone have claimed the deal between the companies should be considered by UK regulators rather than the European Commission (EC), as they are in a better position to analyse the venture.
The Financial Times reports that Orange and T-Mobile's parent companies are more keen to see the EC look at the agreement, as it is thought the authority would take less time to consider it.
Kevin Russell, head of 3 UK, told the newspaper that British authorities were "best positioned" to consider the deal and added that a key concern is the amount of the mobile spectrum that the combined business will own.
He added: "A concentration of 1800 MHz spectrum in the hands of one entity will distort the development of a competitive mobile broadband market."
T-Mobile and Orange signed the final agreement to conclude the creation of the new joint venture at the start of November.