Warren Buffett’s Berkshire Hathaway has reduced its stake in British retailer Tesco to less than 3 per cent, offering a fresh slap to the struggling company.

Buffett’s move, revealed in a regulatory filing on Thursday, was not unexpected.

He told CNBC this month that his investment in the supermarket giant was “a huge mistake by me”.

Buffett’s stake is down from 3.2 per cent earlier this week and 5.1 per cent last year.

The sale comes as Tesco investigates why half year profit was overstated by STG250 million ($A456.33 million).

Eight executives have been swept up into the probe.

Tesco, one of the world’s largest retailers, has issued a series of profit warnings, and its stock price has fallen by about 50 per cent in the past year as it struggles to compete with low cost rivals.

AP