O2 and Virgin Media have started talks for a multi-million merger.
A potential tie-up could create one of the UK’s largest entertainment and telecoms firms.
Spanish firm Telefonica, which owns O2, confirmed that it was in talks with Liberty Global, which has owned Virgin Media since 2013.
02 said the negotiations were ongoing and there was no guarantee they would reach a deal.
“The process initiated by both parties is in a negotiation phase, not being able to guarantee, to this date, neither the precise terms nor the probability of its success,” Telefonica said.
O2, which provides the network for Tesco Mobile, Giffgaff and Sky Mobile, is the UK’s largest phone company with around 34 million users.
Virgin has about six million broadband and cable TV customers and another three million mobile users.