British supermarket Tesco must make wholesale changes to its structure if the company is to turn its fortunes around, analysts at Shore Capital said in a note to investors on Friday.Kantar retail data showed Tesco had underperformed the UK grocery market by more than 12% in the three months to 18 August, as the retailer continues to struggle against discount chains Aldi and Lidl.Tesco has lowered its guidance for profit in the 2015 financial year and it expects it to be between £2.4bn and £2.5bn, a 28% decrease year-on-year, while trading profit in the first half is estimated to be down 31% compared to the same period in 2014.According to Shore Capital, the group's decision to lower guidance, "reflects a further weakening of current trading whilst potentially providing for some resource for a second half fight back".DC