Billionaire investor Warren Buffett has cut his stake in Tesco by more than a quarter which could knock confidence in its turnaround plan.

Buffett has reduced his holding in the supermarket group from 5.2% to 3.7% over the past year, selling 115m shares, it was revealed over the weekend when he filed the accounts of his Berkshire Hathaway investment vehicle.

Buffett did not reveal his reasons for cutting the Tesco stake but it could raise fresh questions over Tesco’s strategy, as Berkshire Hathaway, which also invests in Coca Cola and American Express, is famous for holding its largest equity stakes for a long time.

Last week Tesco chief executive Philip Clarke said he would review the supermarket’s profit margin of 5.2% as it accelerates a revamp of its stores and cuts the price of key products.

Tesco like-for-likes fell 2.4% over the all-important Christmas trading season.