Almost 2.5 million BT customers could receive up to £500 each after a tribunal approved an attempt to launch a class action against the telecoms company over claims it overcharged them for their landline telephone services. The competition appeal tribunal (CAT) has allowed Justin Le Patourel, the founder of consumer group Collective Action on Landlines (Call), to bring the landmark £600m case on behalf of 2.3 million landline-only customers against BT. The group claims the customers, typically from older and low-income households, are owed compensation for payments made between October 2015 and April 2018. “We believe that BT has been overcharging millions of its most loyal customers for years,” said Le Patourel, who has previously worked at the telecoms and media regulator Ofcom. “We think that these customers could be entitled to a substantial repayment of up to £500 each.” The class action will automatically include all affected customers – including those who are now deceased, after BT giving consent to an amendment to the claim – unless they actively choose to opt out. The claim has been filed by the law firm Mishcon de Reya and will proceed to a full trial with a hearing scheduled for 19 October. “We strongly disagree with the speculative claim being brought against us and we will consider all available options,” said a spokesman for BT, which vowed to “vigorously defend itself”. “We take our responsibilities to customers very seriously and will defend ourselves against any claim that suggest otherwise.” However, the three-member tribunal was unanimous in ruling that the claim showed more than enough merit to be pursued. “We conclude that there is a real prospect of success for this claim,” the tribunal concluded in its 42-page ruling. Le Patourel launched the class action this year after looking into an Ofcom investigation into BT in 2017. Ofcom’s scathing investigation found that people who only had a landline telephone were “getting poor value for money in a market that is not serving them well enough”. BT cut the landline charges the following year for 1 million mostly elderly customers by £7 a month but did not offer them compensation for overcharging in the past. “BT regrets being drawn into litigation on a topic Ofcom considered more than three years ago,” said the company “At that time, Ofcom’s final statement made no finding of excessive pricing or breach of competition law more generally.” The company added that it had offered a discounted social tariff for a number of years, and this month had extended it to help a potential 4m households on low incomes.