Vodafone Group and Telefonica have made informal offers worth about £4 billion to Deutsche Telekom to buy its T-Mobile UK, the Financial Times reported.

The companies made cash offers for Deutsche Telekom’s UK mobile unit at the end of last month. Deutsche Telekom is in discussions with France Telecom, Orange UK’s owner, to form a joint venture of their UK assets, the FT reported.

Reportedly, Deutsche Telekom is considering selling its subsidiary after it was hit with £1.6 billion write-down on its mobile division earlier this year.

Currently, T-Mobile is the fourth-largest mobile operator in the UK, with a 15% share of the market, while O2 is the largest UK operator with a 27% share, followed by Vodafone (25%) and Orange (22%).

The takeover of T-Mobile UK by any of the three companies would result in an entity with largest share in the UK market, although the deals run the possibility of being blocked by the competition regulators.

FT reported that Vodafone and Telefonica are considering concessions, in a move to obtain approval from the competition regulators.