Quinn Emanuel Urquhart & Sullivan is building a claim on behalf of BT shareholders and funders against the company over an accounting scandal in its Italian business.

Earlier this month, BT issued a profit warning after it revealed that the impact of the scandal was much worse than originally thought.

BT's share price plunged by around 20% after the bill for mismanagement at its Italian branch almost quadrupled, from £145m to £530m.

Quinn Emanuel London co-managing partner Richard East (pictured) said: "We are in contact with our clients and expect to form a group of substantial institutional investors. We have not decided whether this will be a funded case or whether we will bring this as a damage-based agreement. We confirm that we are in preliminary discussions with both shareholders and a number of funders."

Quinn Emanuel's team includes East, London litigation partner and energy litigation chair Ted Greeno, and EU and German competition law chair Nadine Herman.

Quinn Emanuel is also advising on a record-breaking £14bn claim brought against MasterCard in September, on behalf of 46 million British debit and credit card holders over the company's charging of illegal payment fees. The plaintiffs argue that part of the cost of these fees was passed onto consumers in the form of increased prices for goods and services.

The firm is also advising on a $44bn German investor claim against Volkswagen related to the emissions-rigging scandal the carmaker has been embroiled in, after it emerged that it had been cheating emission tests by using software that made its cars appear less polluting than they are.