Tesco is expected to on Wednesday report its worst set of results in 20 years amid growing competition from smaller discount chains.The UK supermarket is forecast to post a 4% fall in first quarter sales, compared to a 2.9% decline in the previous quarter. The company has tried to win back market share by spending £200m on cutting the price of basic items.However, Kantar Worldpanel revealed on Tuesday that Tesco's sales fell 3.1% year-on-year over the past 12 weeks, giving it a market share of 29%, down from 30.5%.Smaller discount stores such as Lidl and Aldi and premium grocers including Waitrose and Marks & Spencer have hurt sales at its larger peers, including Tesco and Morrison.Clive Back, an analyst at stockbrokers Shore Capital, said he had "never been so gloomy about Tesco's prospects in 20 years"."We believe Tesco UK is increasingly perceived by customers as simply too expensive versus the discounters, Asda and potentially Morrison," he said. "That is a dangerous and frankly untenable place for a mass-market leader to be." Wednesday, June 4thINTERIMSAlternative Networks, OMGINTERIM EX-DIVIDEND DATEArtemis VCT, Associated British Foods, Avingtrans, Blackrock Frontiers Investment Trust, Brewin Dolphin Holdings, Cardiff Property, Daily Mail and General Trust A (Non.V), Debenhams, Edge Performance VCT 'H' Shares, Grainger, Greencore Group, Hargreave Hale AIM VCT 1, Jersey Electricity 'A' Shares, Renew Holdings, Schroder UK Mid Cap FundQUARTERLY EX-DIVIDEND DATEAlbion Technology & General VCTINTERNATIONAL ECONOMIC ANNOUNCEMENTSADP payrolls report (US) (12:15)Balance of Trade (US) (13:30)Beige Book Fed Survey (US) (19:00)Crude Oil Inventories (US) (15:30)GDP (1st release) (EU) (10:00)ISM Non-Manufacturing (US) (15:00)ISM Services (US) (15:00)MBA Mortgage Applications (US) (12:00)PMI Composite (EU) (09:00)PMI Composite (GER) (08:55)PMI Services (EU) (09:00)PMI Services (GER) (08:55)Producer Price Index (EU) (10:00)Productivity (US) (13:30)FINALSAdvanced Computer Software Group, API Group, Findel, RPC Group, Synergy Health, Workspace GroupANNUAL REPORTAEC EducationIMSSTescoSPECIAL EX-DIVIDEND PAYMENT DATEAlliance Trust, Artemis VCT, Evraz, Helios Underwriting, Perpetual Income & Growth Inv Trust, Taylor WimpeyAGMSAfren, Albion Development VCT, Albion Development VCT 'D' Shares, Amara Mining, Cayenne Trust, IG Seismic Services GDR (Reg S), JKX Oil & Gas, KBC Advanced Technologies, Lenta Ltd GDR (Each 5 Repr 1 Ord) (144A) , Mears Group, Proton Power Systems, WANdiscoUK ECONOMIC ANNOUNCEMENTSBRC Shop Price Index (00:01)Official Reserves (09:30)PMI Composite (09:30)PMI Services (09:30)FINAL DIVIDEND PAYMENT DATELegal & General Group, Lookers, Northbridge Industrial Services, SThreeFINAL EX-DIVIDEND DATEAberdeen New Thai Inv Trust, Augean, Bank of Georgia Holdings, Bioquell, Brammer, Cello Group, Christie Group, Cineworld Group, Cupid, Hargreave Hale AIM VCT 2, Headlam Group, Helios Underwriting, Inspired Energy, Irish Continental Group Units, JPMorgan Euro Small Co. Trust, Judges Scientific, Keller Group, Laird, London & Associated Properties, M&C Saatchi, Marshalls, Mckay Securities, Moss Bros Group, National Grid, Nationwide Accident Repair Services, Octopus VCT 2, Pace, Proven Planned Exit VCT, Quarto Group Inc., Rotala, Slingsby H.C, Staffline Group, Synthomer, WPP, Young & Co's Brewery 'A' SharesRD