THE The crisis at Tesco is a national interest issue that will affect the whole British business community, shadow business secretary Chuka Umunna has said.

Mr Umunna said he was "deeply troubled" by the revelations of an accounting error which inflated the supermarket giant's profits by £250 million.

And he said it was important to know whether the incident - which has led to the suspension of four executives while an investigation takes place - was an isolated incident or part of a pattern.

"I'm deeply troubled by what it transpired has happened," he said.

"It is quite something to overstate your interim results by £250 million and this isn't any company, this is Tesco - one of the best-known British brands, our biggest supermarket.

"It is very difficult for us to make a judgment right now as to whether any public policy issues have been engaged by what has happened.

"We need to see what the report by Deloitte - who have been appointed by Tesco to investigate what happened - throws up.

"But whilst it may not, at first instance, be a public policy issue, it is definitely a national interest issue and this will have an impact on our business community.

"I just hope that this is a one-off and this hasn't been something that has been happening at Tesco over a period of time."

The arrival of a new finance director failed to put the brake on Tesco's falling share price yesterday as more details emerged of a grim summer of trading.

Closely-watched data from Kantar Worldpanel put the grocery chain's market share at 28.8 per cent in the 12 weeks to September 14, after a 4.5 per cent fall in sales.

The retailer, whose share of the market was above 30 per cent last year, is in the grips of major crisis after it emerged yesterday that it had over-stated its profits guidance to the City by an estimated £250m.

The fourth profits warning of the year sent Tesco shares down by 12 per cent to their lowest level in a decade yesterday, with no respite for the stock today despite the arrival of a new finance director.

Alan Stewart will join the board with immediate effect after Tesco struck a deal for his early release from Marks & Spencer. He resigned from M&S in July but had not been due to start at Tesco until December 1, even though his predecessor Laurie McIlwee handed in his notice in April and left Tesco this summer.

The supermarket's new chief executive, Dave Lewis, only started in the job at the beginning of September.

Mr Stewart began his career in investment banking with HSBC before joining Thomas Cook, where he was appointed UK chief executive in 2001. He also worked for WH Smith prior to his move to Marks & Spencer in 2010.

Tesco has suspended four executives in its UK business while it investigates the over-statement of profits. The inquiry will look into the way it treated rebates paid by suppliers and whether they were reported in the right time period.