Three has filed its long-threatened legal challenge to telecoms regulator Ofcom over the rules it has established to govern the forthcoming auction of mobile spectrum.
Three this week formally filed its legal challenge, which threatens Ofcom over its "meaningless" 37 per cent spectrum cap.
Ofcom announced the cap back in July, which means that BT and Vodafone, which currently own 45 per cent and 28 per cent of the spectrum currently available, will be restricted in how much of the critical 5G spectrum they can buy up later this year.
At the time, Three - which had called for a 30 per cent cap - described the decision it as a "kick in the teeth for all consumers" and claimed that Ofcom is "damaging competition, restricting choice and pushing prices up for the very consumers that it is meant to protect."
After last month threatening Ofcom will legal action the operator this week kicked off a judicial review that will last at least three months.
The firm argues that Ofcom's promised plans "fail completely to achieve… the decision's own basic objective of avoiding very asymmetric spectrum shares," adding that the proposed auction rules mean that BT could have a share of more than 39 per cent until 2020.
"We confirm that we have filed a judicial review before the UK courts in relation to the competition measures that will apply in the upcoming spectrum auction," a Three spokesperson said.
"It is absolutely vital that the regulator gets this auction right for the long-term benefit of all consumers."
However, Three's larger rival Vodafone has slammed Three's legal challenge, claiming that it will "unnecessarily delay" the process.
In a statement to the Financial Times, a spokesperson added: "This is not in the interest of consumers and will undermine the UK's efforts to be a leading digital economy."
Ofcom, meanwhile, described the challenge as "very regrettable", and confirmed Vodafone's claim that it would delay the auction.
It continued: "The auction will now be delayed by this litigation, which will harm consumers, businesses and ultimately the UK economy. It is now crucial that companies don't drag their feet, so the case can be heard as soon as possible."
BT-owned EE is also expected to launch its own legal challenge, having previously claimed that Three's attempt to lower the overall cap will damage its ability to bid in a spectrum auction in 2019 for frequencies used in 5G technology
"In response to Three's action, we have made the difficult decision to challenge the proposed structure of the next auction of mobile spectrum.
"We need to protect our customers' mobile experience, and help build the platform for the UK to have the highest quality 5G networks," EE said in a statement last month.
The FT notes that EE still has a number of weeks to file its claim for judicial review.
Wikileaks Vault 7 suspect Joshua Schulte fingered by FBI after re-using smartphone passwords on his PCs
Joshua Schulte indicted on 13 counts relating to Vault 7 leaks and trading in images of child abuse
Alexa for Hospitality will link with existing systems so guests can order room service and control the air con
Massive volcanic eruptions could have warmed Mars' surface sufficiently for oceans to form
Examination of fruit flies' brains generated more than one billion data points for scientists to analyse