BT's £12.5 billon buyout of mobile phone giant EE has been given the go-ahead after a six-month inquiry by the competition regulator. But if you're an EE customer, you won't see any change to your contract when the merger goes ahead, probably at the end of this month.

The landmark deal will see BT take on all of EE's 24.5 million mobile and 800,000 broadband customers, and once the takeover's completed the combined companies will have around 35 million mobile, broadband and TV customers.

The Competition and Markets Authority (CMA) today announced it had approved the deal, with its inquiry concluding the merger is unlikely "to cause significant harm to competition or the interests of consumers".

But competitors in the telecoms industry have warned the merger will create a new "dominant" player.

What will the deal mean for customers?

Existing EE mobile and broadband customers will remain EE customers. They won't see any change to their contracts – eg, allowances, prices and contract lengths – when the merger's completed, which is expected to be on 29 January.

An EE spokesperson has also told MoneySavingExpert that BT plans to continue operating the EE brand, so the name on your bill won't change either.

However, the merger could mean a wider range of deals for new customers, potentially including 'quad play' deals, where you have a single contract covering home phone, broadband, mobile and TV. See our Cheap Mobiles guide for the current top pick deals.

BT's takeover of EE given green light
BT's takeover of EE given green light

What did the CMA review find?

The CMA found the deal is unlikely to harm competition or customers.

John Wotton, who chaired the inquiry, says: "The retail mobile services market in the UK is competitive, with four main mobile providers and a substantial number of smaller operators.

"As BT is a smaller operator in mobile, it is unlikely the merger will have a significant effect. Similarly, EE is only a minor player in retail broadband, so again it is unlikely the merger will have a significant effect in this market."

What do the big telecoms companies say?

BT's chief executive Gavin Patterson has hailed the deal as a "major milestone".

He says: "The UK's leading 4G network will now dovetail with the UK's biggest fibre network, helping to create the leading converged communications provider in the UK. Consumers and businesses will benefit from new products and services as well as from increased investment and innovation."

But a spokesperson for rival TalkTalk said: "We are disappointed, although not surprised, that the CMA has waived through the BT/EE merger, even though the new entity will be even more dominant than it was before privatisation 30 years ago."