The lawsuit was filed on Thursday in New York federal court, the same day the company reported a bigger than expected hole in its finances, prompting its chairman to resign.

The lawsuit was brought by Irving Fireman's Relief and Retirement Fund on behalf of purchasers of Tesco's American depository shares from Feb. 2 to Sept. 22.

The lawsuit accused Tesco and former executives, former Chief Executive Officer Philip Clarke and ex-Chief Financial Officer Laurie McIlwee, of making false and misleading statements and failing "to disclose the truth regarding the company's financial condition."

The lawsuit cited Tesco's surprise announcement on Sept. 22 that it had overstated first-half profits by 250 million pounds ($402 million).

The announcement prompted Tesco's American depository shares to fall 15 percent to $9.61 from its price the previous Friday, the lawsuit said.

A representative for Tesco declined comment.

The complaint did not reference Tesco's more recent announcement on Thursday that it had overall incorrectly booked income of 263 million pounds ($421 million), up from the original estimate of 250 million pounds.

Of the 263 million pounds, around 145 million came from prior years, Tesco said. A spokesman said on Thursday the figure was not big enough to require those previous results to be restated.

Britain's accounting watchdog, the Financial Reporting Council, said on Thursday it was looking into Tesco's announcement of accounting irregularities to determine whether it should take regulatory action.[

The case is Irving Firemen's Relief and Retirement Fund v. Tesco Plc, U.S. District Court, Southern District of New York, No. 14-8495.

(Reporting by Nate Raymond in New York; Addtional reporting by Kate Holton in London; Editing by Chris Reese)

By Nate Raymond