The Competition and Markets Authority has given the green light to BT's £12.5bn takeover of Britain's biggest mobile operator, EE.
The CMA has decided the deal would not cause significant harm to competition in any of 10 markets investigated, despite consternation among rivals about BT's control of connections for mobile masts and wholesale mobile capacity for virtual networks.
John Wooton, chair of the CMA inquiry, said: "We provisionally think that the retail mobile market in the UK, with four main mobile providers and a substantial number of smaller operators, is competitive."
"The group does not provisionally believe that, in a dynamic and evolving sector, it is more likely than not that BT/EE will be able to use its position to damage competition or the interests of consumers."
The CMA pointed out that EE is a relatively small player in the fixed-line broadband market, while BT is currently a relatively small mobile player.
BT chief executive Gavin Patterson said: "We're pleased that the CMA has provisionally approved BT's acquisition of EE. The combined BT and EE will be good for the UK, providing investment and ensuring consumers and businesses can benefit from further innovation in a highly competitive market."