Sir Terry Leahy, the former boss of Tesco, has said he is "very disappointed" with the recent sales performance of the grocer.The comments follow the group's first-quarter results last week, which revealed that UK like-for-like (LFL) sales excluding petrol slid 3.7%. This was a deterioration from the -2.9% LFL exit rate in the fourth quarter and the supermarket's worst quarterly figures in 40 years.Leahy, who left in 2011 after 14 years at the company, said in an interview with Sky's Ian King Live programme: "As a shareholder I am very disappointed."The sales decline was blamed on Tesco's recent string of price cuts as the Big Four continue to lose market share to the cheaper, so-called 'discounter' retail chains such as Aldi and Lidl. The company also said it saw a "continuation of the challenging consumer trends in the UK", it said on June 4th."I know the business will be disappointed and the board will be keen to take whatever action is necessary in order to improve the situation," Leahy said."Tesco is a great business and it's a great employer. We need to see it back with confidence and growing again."Leahy, who helped turn Tesco into the third-largest retailer in the world by revenues, is set to make a return to the stock market as Chairman of soon-to-be-listed discount retailer B&M Retail, valued at just under £3bn.BC