The Competition and Markets Authority (CMA) has begun looking into BT's £12.5 billion takeover of 4G mobile broadband provider EE.
As reported by the Financial Times, the watchdog is seeking "early views" on the impact of the intended acquisition on the UK telecoms sector.
The CMA has sent letters to industry stakeholders - including rival broadband providers - as it gears up to launch a full merger inquiry.
In a letter seen by the news provider, the CMA highlighted several areas that could suffer a “potential impact” from BT’s acquisition of EE.
These included the market for fixed and mobile broadband services, and the way BT provides connections between mobile masts for network operators.
The CMA has also asked for any concerns about BT's ability to introduce quad-play broadband packages, which offer fixed-line internet, home phone, mobile and TV services.
A spokesperson for BT said the company is "pleased" the CMA has begun to ask telecoms operators for their views.
"This was always going to be part of the process, and we welcome the fact that the industry is being given an early opportunity to provide comments," the representative stated.
"We believe the proposed acquisition will be positive for consumers, businesses and the UK, with BT creating a world-class digital infrastructure for Britain."