Buffett, often referred to as the Oracle of Omaha, has consistently backed Tesco, holding a stake in the firm since 2007. But his investment firm Berkshire Hathaway is now dealing with a hefty loss after the retailer slumped over 20 percent in the last month.
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On Monday alone, Tesco shares plunged almost 12 percent after the company announced that it had apparently overstated its half-yearly earnings by £250 million ($407 million).
According to Berkshire Hathaway's annual letter to shareholders, which reports the changes in its equity positions that exceed $1 billion, Buffett owned 301,046,076 shares in the retailer - or 3.7 percent of the company - at the end of 2013.
The supermarket was the only stock in his top 15 picks that posted a loss in 2013. The shares were purchased for $1.699 billion, and according to Buffet's letter were worth $1.666 billion at the end of last year.
The slide in Tesco's share price this year means that, since last December, Buffett's loss on the shares stands at around $716 million, providing he currently owns a similar number of shares in the group.
Ratings agency Standard & Poor's put the retailer on a negative credit watch on Wednesday following the chain's apparent accounting miscalculation, until Tesco announces its interim results, which have been delayed until late October.
Some investors are using the price slump as an opportunity to snap up shares in the grocer, notably U.K. businessman and chief shareholder of Sports Direct, Mike Ashley.
Ashley is betting Tesco shares will bounce back from their 11-year low through a put option for 23 million shares with Goldman Sachs, putting the group's maximum exposure to the grocer at around £43 million.