‘Ambulance chasers’ eye troubled Tesco

U.S. law firms are appealing for burnt investors in Tesco to get in touch, after the U.K. supermarket giant revealed last week it had overstated first-half profit by £250 million ($405 million).

Tesco said on Wednesday that Britain's financial watchdog was launching a full investigation into the accounting scandal, which has seen Tesco shares fall by around 21 percent to 180.8 pence. Tesco has suspended four senior executives and launched its own investigation, calling in forensic accountants and lawyers.

Read MoreUK watchdog launches investigation into Tesco

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Earlier this week, litigation specialist Kahn Swick & Foti said it had started investigations into Tesco, focusing on whether the company violated U.S. federal securities law. It appealed to investors get in touch via phone or email if they had suffered losses or had information that could assist investigations.

"KSF's investigation is focused on Tesco's… disclosure that the company is investigating the overstatement of its profit forecast for 2015 by approximately $408.8 million," the law firm said in press release on its website.

Read MoreTesco's execs suspended in $409m profit probe

Los Angeles-based Glancy Binkow & Goldberg made a similar appeal. "If you purchased Tesco ADRs (American Depositary Receipts), if you have information, or would like to learn more, or have any questions concerning this announcement or your rights or interests with respect to these matters, please contact Lesley Portnoy, Esquire, of Glancy Binkow & Goldberg."

Legal professionals and academics told CNBC it was difficult to assess the likely outcome of such suits until Tesco wrapped up its own investigation. The company has appointed auditors from Deloitte to conduct investigations.

'Ahead of the game'

"The law firms are trying to get ahead of the game," said Stephen Ross, head of civil fraud group litigation and arbitration department at Withers in London. "They're seeing if they can sign up enough people to bring proceedings."

Class action suits—legal action brought by a large number of people—are easier to get off the ground in the U.S. rather than the U.K., according to Ross. "It's easier to get people on board … you have to get people to opt in here, but in some U.S. states it's more of an opt out."

Tesco declined to comment on the matter.

"This is your classic class action ambulance chasers," Tony Williams, founder of London law consultancy Jomati Consultants, told CNBC in a telephone interview. "When they say an 'investigation', they're trying to get a few people together to do a class action and litigate."

Williams added: "The minute companies have a profit warning or anything else, you'll see these king of adverts trying to get a class action going … most of them peter out but sometimes they score."

Read MoreBuffett loses big on Tesco share dive

Andrew Johnston, a specialist in company law and corporate governance at Sheffield University, doubted the law firms would be successful if they litigated.

"There isn't a very strong incentive for minority shareholders to litigate," Johnston told CNBC in a telephone interview. "They won't be able to prove fraud, and negligence won't give them the remedy they want."

Earlier this year, a U.S. judge ruled that a group of shareholders in BP—a FTSE 100-listed company like Tesco—could pursue a class action lawsuit against the oil giant. The shareholders say the oil giant mislead them by understating the severity of the 2010 Gulf of Mexico oil spill.

The Tesco scandal comes as the supermarket continues to struggle with falling sales and declining market share. British shoppers are increasingly opting for discount rivals such as Aldi and Lidl. Sales at Tesco fell 4.5 percent in the 12 weeks to September 15 compared to the same period in 2013, according to research provider Kantar World.

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