The UK’s Competition and Markets Authority (CMA) has launched a phase 1 investigation into the merger of secondary ticketing firms Viagogo and StubHub in a $4bn deal.

The watchdog is looking into whether the deal will result in a “substantial lessening of competition within the market,” by looking at the provisions of the Enterprise Act 2002.

The CMA is inviting comments on the transaction from any interested party before January 10, 2020, prior to the start of the merger.

Earlier this month, anti-touting campaign group FanFair Alliance, called on the UK’s competition watchdog to launch a probe into the proposed buyout.

Viagogo and eBay stunned the live entertainment industry when they announced the mega deal last month. The two parties said it is likely to close by the end of the first quarter of 2020, subject to regulatory approval.

Adam Webb, campaign manager, FanFair Alliance, said: “Having written to the CMA and urged them to investigate, we’re obviously pleased they’ve opened a Phase 1 inquiry.

“Aside from the persistent controversies surrounding these platforms, both of which are almost wholly dependent upon large-scale commercial ticket resellers, a merger between Viagogo and StubHub would have profound and damaging impacts for UK audiences and music businesses.”

Both Viagogo and StubHub have attracted the focus of regulators in recent years, with the former in particular having been criticised and sanctioned by watchdogs in the UK and other jurisdictions.

The UK’s competition regulator suspended preparations for court action against Viagogo earlier this year after ruling that Viagogo had finally addressed its outstanding concerns about how it presents important information to its customers, claiming it is “worlds apart from the one they faced before the CMA took action.”

A Viagogo spokesperson said: “It’s customary for regulators to review acquisitions of this size. We will work collaboratively with the CMA to address any of the enquiries.”