A takeover bid for the Isle of Wight Festival is being investigated by a watchdog amid concerns over the deal.
The inquiry comes after bidder Live Nation said it had become the majority shareholder of the event in March.
The Competition and Markets Authority (CMA) is investigating whether the takeover would lead to a “substantial lessening of competition”.
It said it had asked Live Nation and the festival to operate separately until it had agreed any merger.
Live Nation, which has refused to comment, moved to take up a controlling stake of the festival through LN-Gaiety – its UK joint venture with music mogul Denis Desmond’s Gaiety Investments.
Announcing the plan last month, Mr Desmond said it was “fantastic” to add it to its portfolio of more than 85 music festivals worldwide, including Reading, Leeds, Wireless and T in in the Park.
Isle of Wight Festival founder John Giddings said the partnership would “give us the ability to access the company’s scale and talent pool, bringing more acts and a better experience to the UK”.
Live Nation has been on a buying spree recently, making eight major acquisitions worldwide in 2016, while the Isle of Wight Festival deal marked its sixth so far this year.
The CMA said it had not yet set a date for consultation submissions or its decision.
In October, organisers threatened to cancel this June’s event unless fee changes were agreed with Solo Promoters Ltd.
But the following month, Sir Rod Stewart was revealed as the headliner.
It is expected to attract about 42,000 fans, with other acts including DJ David Guetta, indie-pop group Bastille and singer-songwriter George Ezra announced.
Mr Giddings revived the festival in 2002 after a 32-year hiatus.
It first started in 1968, with guitarist Jimi Hendrix making a headline performance in 1970.