BT's handle on the national network has once again come into question, with rivals arguing that the current landscape is leading to a "substandard experience for millions of customers".
In a letter published in the Financial Times, a group – which includes Sky, Vodafone and TalkTalk – suggests a "radical reform" is required due to "fundamental problems" that cannot be resolved by "tinkering with the existing regulatory framework".
"It is therefore crucial that Ofcom moves as quickly as possible to ask the Competition and Markets Authority (CMA), with its far-reaching powers, to undertake a full market investigation," it read.
The groups reiterated their calls for BT's Openreach division to be made separate from the rest of the group, claiming this will improve their access to the national broadband network that they need to sell internet packages to their customers.
As things stand, there is a "diminished opportunity for alternative providers to compete effectively," the letter argued.
The document, co-signed by both the Association of Independent Professionals and the Self Employed, is the latest attempt by BT's rivals to convince the competition watchdog that the British telecoms group is providing a poor service to their internet businesses and under-investing in the network.
While BT acknowledged that there is room for improvement in terms of customer service, it was quick to highlight that Openreach is exceeding all 60 of the service targets set by Ofcom.
"It would lead to huge uncertainty and fundamentally undermine the case for future investment, dragging the UK backwards at the very time it needs important investment in its infrastructure," it protested.