The UK Competition and Markets Authority (CMA) has provisionally ruled that the proposed acquisition of Substantial by Nexfibre qualifies as a relevant merger situation and could weaken competition in the UK wholesale fixed broadband services market.

The watchdog's provisional findings, which now go to the interested parties, set a deadline of 23 October for responses. That consultation step will shape whether the CMA moves to a full phase of scrutiny or extracts remedies before clearing the transaction.

The deal under examination is unusual in structure. Substantial is a holding company that houses FTTP network operators Netomnia and Brsk, alongside retail fibre broadband provider YouFibre. Nexfibre, the would-be acquirer, is a wholesale fibre network operator. A combined entity would therefore bring together two of the larger independent full-fibre builders in the UK and fold a retail arm into a wholesale platform, a vertical integration that sits at the centre of the CMA's concerns.

The specific worry identified provisionally is the wholesale fixed broadband services market. Altnets such as Netomnia, Brsk and Nexfibre increasingly sell wholesale access to their fibre-to-the-premises networks, competing not only with each other but with Openreach, BT's infrastructure arm, as retail ISPs seek alternative upstream suppliers. Removing one head-to-head wholesale competitor through merger could, in the CMA's provisional view, reduce the competitive pressure that has shaped pricing and terms in this segment.

The provisional RMS designation is a procedural but consequential finding. By establishing that the transaction constitutes a relevant merger situation under UK merger control rules, the CMA confirms its jurisdiction and its authority to assess — and if necessary block or condition — the combination. The next substantive question is whether the regulator's final findings echo the provisional concern about reduced competition, or whether the parties can offer commitments sufficient to address it.

For the companies involved, the stakes are considerable. Nexfibre has positioned itself as a wholesale-only fibre operator, while Netomnia and Brsk have been among the most active builders in the crowded UK altnet field, and YouFibre gives the group a retail channel to monetise its network directly. Consolidation among UK altnets has been widely anticipated as the sector matures and funding tightens, and this transaction is one of the most significant tests yet of how the CMA will treat fibre market concentration.

The parties now have until 23 October to make their case to the regulator, after which the CMA will weigh the submissions before issuing its next decision on whether the merger should proceed, and on what terms.