According to a survey to be published this week by the research group Verdict, prices at the quality supermarkets have fallen 7 per cent since last September, compared with a 3 per cent drop at the discounters.
Verdict cautions against calling the latest moves a price war, saying the cuts are selective.
But it says there has been a marked acceleration in the growth of the discount sector of the market.
Sales at discount chains were worth more than pounds 4bn in 1992 compared with pounds 2bn in 1983.
The French supermarket chain Carrefour recently opened its first British outlet in Kent and has targeted London and the South-east for further expansion. Traditionally discounters have concentrated on the North of England and Scotland.