There was more bad news for Tesco on Tuesday as latest data showed another drop in its sales and market share only a day after an accounting gaffe forced it to revise its profit forecasts.Tesco's sales went down 4.5% and market share dropped to 28.8% from 30.2%, according to latest figures from retail research group Kantar Worldpanel.The news came a day after Tesco was forced to call in investigators and suspend four senior executives as it discovered it had over-estimated its profit forecast by £250m.More than £2bn was wiped off the group's value during Monday trading after chief executive Dave Lewis admitted accountants and lawyers had been summoned to scrutinise the company's books following revelations that payments from suppliers were being mis-booked.The news makes "further grim reading for Tesco," Zeus Capital retailing analyst and consultant Nick Bubb said.Kantar said on Tuesday the grocery market slowed to a new record low of 0.3% this year. It followed a twelfth successive fall in inflation, which now stands at 0% for the 12 weeks ended 14 September.The panel said Asda registered the best results among the big four supermarkets, which also include Tesco, Sainsbury's and Morrisons, and was the only one which managed to increase its market share. Market share rose 17.4% this year while sales grew 0.8% year-on-year.Morrisons is also facing difficulties, with sales down by 1.3% for the year.Sainsbury's saw a decrease in its market share to 16.2% from 16.6% last year, while its sales decreased by 1.8%.Aldi saw an increase in its sales by 29.1% for the year ended in September compared to the previous year. Lidl has also raised its sales by 17.7% due to its discounts.Fraser McKevitt, head of retail and consumer insight at Kantar, said: "For the first time ever we've seen the average basket of everyday goods bought today costing exactly the same as it did a year ago."With some staple groceries such as vegetables, milk and bread prices are actually falling as the big retailers all compete for a bigger slice of shoppers' wallets."