"Some roles" might be impacted by the merger with Three, Ahmed Essam said, in his first interview since the deal was struck last week.

If the merger gets regulatory approval it would create a mobile phone network with 27 million customers. But the Competition and Markets Authority (CMA) must first review the deal and likely will be concerned about reduced competition for consumers shopping for a provider.

Job losses were also raised as a concern by Unite, the union. It said the deal was a "reckless merger" that would mean losses for workers at both companies. Up to 1,600 jobs could go, Unite added.

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There are opportunities for reskilling as part of the investment that the companies plan to make through the merger, Mr Essam said.

"So it's very early today to talk about job losses, but clearly this case is about investment. And with investment there will be direct and indirect benefit from employment."

Any "impacted roles" would go through "proper consultation and proper process", he added, but said there is also "a lot of room for reskilling".

"There's a lot of room to to reinvest in the network and deploy resources where it can add value."

An £11bn investment has been promised by executives over the next 10 years along with the creation of 8,000 and 12,000 new jobs in the wider economy.

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The money will go towards building a "best-in-class" 5G network, Three and Vodafone said.

It is because of the benefit to consumers that Mr Essam said he believes regulators will approve the deal. It will add a "third big challenger" to providers O2 and BT-owned EE, he said.

"What this brings is it actually elevates the quality of the network."

The proposed merger will also test a new national security law, as Three is owned by the Hong Kong-based CK Hutchison. Boris Johnson's government brought in the legislation to have oversite of international takeovers of UK companies that are believed to be a threat to national security.

Mr Essam said he was "confident" the merger will clear the legislative hurdle.

"Both businesses today are operating in the UK, both businesses are subject to the same regulation," he said.

"We're quite confident that we have a strong case and we have solid compliance when it comes to security".