Sales of £1 packs of grapes increased by 550% and potatoes by 250% in the last promotional period, said Musgrave Retail Partners GB marketing director Jemima Bird.
The scheme, which covers at least five fresh produce items every three-weekly promotional period, had worked so well that it was now being extended to Londis retailers, she added.
Retailer Kevin Whalley, who owns three Budgens stores in Chalfont St Peter, Bedfont and Langley, said the £1 offer was a fantastic tool to drive sales. "This gives customers just what they're looking for - the perception of great value - and we've seen huge uplifts in sales as a result," he added.
The £1 deals are supported with a point-of-sale package that includes banners, wobblers, hanging arrows and posters.
A growing number of retailers are now choosing the £1 promotional mechanic over more traditional bogof deals.