Tesco now has 40% or more of supermarket shopping space in 21 UK postcode areas, according to research carried out by Channel 4 TV programme Dispatches.
The findings, aired earlier this week, also show that Sainsbury's has a dominant share in six areas and Asda in one, although once new stores in the pipeline are developed Tesco will move past the 40% share mark in yet another
district, and Asda will control another two.
If anything, the figures understate Tesco's dominance as they do not include ownership of convenience stores.
Development of Tesco's land bank in the Cambridge area will give it 61% of one-stop space locally, according to the study.
In Dumfries and Galloway its share could hit 68%, and in both the Uxbridge and Inverness postcode areas its share could reach 76%.