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Speaking to CNBC on Thursday, the Omaha businessman said: "I made a mistake on Tesco. That was a huge mistake by me."
Buffett is Tesco's fourth biggest shareholders since he started buying the supermarket's shares in 2007. In 2013, he owned 301 million shares, about 3.7% of the company, the FT reported.
According CNBC, Buffett has lost over $700 million on his investment.
Tesco is struggling to compete with other discounts retailers like Aldi and Lidl, and its shares are at a 11-year low. The share price dropped by 49% this year and received a further blow last month when the retailer announced it had overstated its profits by 250 million pounds.