“There is an 80% overlap between these two players and, if the deal goes ahead, it would significantly reduce competition and the choice available to consumers, as well as force hundreds of thousands of Netomnia customers back to VMO2. Given the scale of this overlap, the CMA must thoroughly examine the deal,” Holden said.

He added: “Competition has driven lower prices, faster speeds and better services and this deal risks re-establishing an ineffective duopoly of BT and VMO2 and undermining the significant progress the UK has made.”

The nexfibre deal involves the joint venture acquiring Substantial Group, the UK’s second-largest alternative fibre provider, in a transaction valued at £2 billion.

Substantial Group operates the Netomnia network, currently passing around 3 million premises, with roughly 450,000 customers. Post-close, coverage is expected to rise to 3.4 million premises and more than 500,000 customers.

The transaction is designed to create a scaled wholesale challenger to BT Openreach, combining Netomnia’s network with 2.1 million Virgin Media O2 premises, which nexfibre will upgrade to full fibre. When combined with Virgin Media O2’s wider fibre rollout, the merged platform could reach around 20 million premises, giving ISPs a significant alternative to the incumbent.

Despite the potential market impact, nexfibre has argued the deal will drive innovation and support sustainable wholesale competition.

Rajiv Datta, CEO of nexfibre, previously said: “This transaction creates the largest alternative fibre platform in the UK, establishing the foundation for much-needed altnet consolidation, and sustainable wholesale competition. It will help drive innovation and deliver the economic and societal benefits that full fibre connectivity makes possible.”

Jeremy Chelot, Group CEO of Substantial Group, also emphasised that its retail brand, YouFibre, will continue to operate post-close, ensuring existing customers remain supported while benefiting from the scale and financial strength of the combined infrastructure.

The deal is expected to complete by Q3 2026, subject to regulatory approvals. The Competition and Markets Authority (CMA) will be closely watching the merger, with industry stakeholders like CityFibre urging a thorough review to ensure that UK consumers continue to benefit from competitive pricing, service quality, and choice.

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