The UK's Competition and Markets Authority (CMA) has provisionally found that the proposed merger between wholesale fibre operator Nexfibre and altnet Netomnia would reduce competition in the UK broadband market.

Nexfibre is the fibre-to-the-premises (FTTP) wholesale joint venture backed by Liberty Global, Telefónica — through Virgin Media O2 — and infrastructure investor InfraVia. It builds and operates wholesale full-fibre networks used by retail ISPs, and is closely linked to Virgin Media O2's footprint.

Netomnia is one of the UK's largest alternative network operators, deploying its own FTTP infrastructure to residential and business premises across regions where Virgin Media O2 and Openreach have historically dominated.

The CMA's conclusion is a pivotal regulatory moment for two of the most capital-intensive fibre groups in the UK.

Under UK merger rules, when the CMA finds that a deal is likely to reduce competition, the merging parties typically must propose remedies. These can include structural divestitures (the sale of overlapping network footprints), behavioural undertakings such as guaranteed wholesale access terms, or a combination. Without acceptable remedies, the CMA can block the transaction outright.

The decision sits within a broader pattern of UK fibre-sector consolidation. Independent altnets raised billions in private capital on the assumption that large-scale FTTP rollouts would translate into profitable retail market share. Slower take-up, rising build costs, and aggressive Openreach pricing have forced many of those companies into mergers or restructuring.

The CMA has signalled repeatedly that it intends to scrutinise such transactions closely. Its aim is to ensure that consolidation does not entrench Openreach's position as the dominant UK wholesale access provider.

What is at stake for Nexfibre and Netomnia?

The provisional finding introduces uncertainty over the merger's completion timeline and final structure. Both companies have invested heavily in overlapping regional footprints. Any structural remedy could require divestiture of parts of one or both networks. For Netomnia's privately placed investors, the ruling raises the prospect of a renegotiated deal or a drawn-out process.

How does the CMA reach such a finding?

The regulator's merger review typically proceeds in two phases. An initial phase 1 review determines whether a deal raises competition concerns requiring fuller examination. If so, the CMA moves to a phase 2 investigation, ending in a provisional decision subject to consultation before reaching a final ruling.

What could the remedies look like?

The CMA has a standard toolkit. It can require the merged entity to divest overlapping fibre footprints to a third-party wholesale operator. It can also require the merged entity to commit to open wholesale access on regulated terms. Past UK telecoms mergers have produced a mix of both.

What is the wider market context?

The UK has moved from a position where more than a dozen independent altnets competed to build full-fibre networks, to one where M&A activity is reshaping the field.

Nexfibre itself was formed through consolidation of existing fibre assets under a single wholesale banner. A Nexfibre-Netomnia combination would have created the largest non-Openreach fibre footprint in the country — precisely why the CMA has intervened.

Whether the deal ultimately closes will depend on the remedies Nexfibre and Netomnia put forward. It will also depend on the CMA's assessment of whether those remedies adequately preserve retail-level competition across the overlapping footprint.