BT has successfully defended itself in a £1.3 billion ($1.6bn) class action lawsuit that alleged the telco overcharged millions of customers for fixed telephone lines.

The case, which lasted for eight weeks and began in January, accused BT of overcharging around 3.7 million landline customers.

A verdict was only reached last week by the Competition Appeal Tribunal, as detailed in a 301-page document.

The case against BT was led by former Ofcom official Justin Le Patourel, who alleged BT took advantage of a dominant market position to charge “excessive” prices for landline customers, many of them elderly.

"We take our responsibilities to all of our customers very seriously and welcome today's ruling," said BT in a brief statement.

Le Patourel's case against BT dated back to the period between 2009 and 2017, where the claimants alleged BT unfairly charged customers who took a standalone fixed voice (SFV) connection during this period before British telecoms regulator Ofcom stepped in.

If the verdict had gone against BT, it could be worth as much as £400 ($501) per customer.

Following Ofcom's intervention, BT agreed to lower its prices in 2018, but that didn't stop a class action lawsuit being launched in 2021 by Le Patourel.

However, the Competition Appeal Tribunal sided with BT, despite acknowledging that the telco had significantly and persistently charged excessive prices, but said this was not done unfairly.

The tribunal found that BT had not abused its market position.

“While I am pleased that the tribunal has recognized BT’s dominant position in the market, and the significant and persistent nature of its excessive pricing, I am disappointed that it did not agree that these prices were unfair,” said Le Patourel, who is considering a possible appeal.

Le Patourel worked at Ofcom from 2003 through to 2016. During his tenure, he held senior roles, including head of market intelligence, and consumer policy and protection principal.