LONDON: Tesco cut its profit forecast for the third time this year and suspended four members of staff after finding a fault in its accounts, another blow to the reputation of Britain’s biggest grocer.

The company’s shares fell 12 percent after Tesco said it had called in new accountants to investigate an error that forced it to cut its first-half profit outlook by 250 million pounds ($408.50 million). A profit warning on Aug. 29 had overstated expected first half profit by 23 percent, it said.

The error — caused by an early booking of revenue and delayed recognition of costs — had been discovered during preparation for its forthcoming interim results, Tesco said.

Their publication has now been pushed back from Oct.1 to Oct 23 by the firm’s new chief executive Dave Lewis, who said on Monday that an “informed employee” had notified Tesco’s legal team of the accounting issue on Friday.

Lewis said four Tesco employees had been “asked to step aside” while investigations continue, but had not been disciplined.

He said it was too soon to say whether this was a case of fraud.

The BBC and Sky News reported that Chris Bush, the managing director of Tesco’s UK business, was one of the four.

Lewis declined to comment on Bush but said Robin Terrell, the firm’s multi-channel director, had stepped in to run the UK business.

“We have uncovered a serious issue and have responded accordingly. The chairman and I have acted quickly to establish a comprehensive independent investigation,” he said. “The board, my colleagues, our customers and I expect Tesco to operate with integrity and transparency and we will take decisive action as the results of the investigation become clear.”

Shore Capital analyst Clive Black said he was “flabbergasted” by the latest development and was reviewing his current recommendation to hold the company’s shares.

Tesco said it was working to establish the extent of the issues and the impact they might have on its full-year profit.

“It looks like it’s substantially a first half year (issue) and has more to do with timing, of when income is recognized,” said Lewis.

Tesco has appointed a new tax adviser Deloitte to undertake an independent and comprehensive review of the issues, working closely with Freshfields, its external legal advisers.