Ofcom said it was satisfied that consumers were well served thanks to competition between the country’s five mobile carriers, but this situation could change if the merger were to go ahead.
The regulator has no direct authority to approve mergers but it said it expected to provide input to the relevant authorities.
Ofcom said this matter fell under the European Commission’s jurisdiction and the parties had signalled their intention to file a submission with the EC, which might refer it back to the Office of Fair Trading.
Orange and T-Mobile signed an agreement last month to form a 50-50 joint venture that would grab the top spot in Britain with a market share of 37 per cent.
Ofcom said most stakeholders who provided input for a report on the state of the mobile market agreed that a full market review was not currently required, although some had said this might need to be reconsidered if the market structure changed.
A merger could lead to improved coverage and network quality, Orange and T-Mobile have said.