The number of products sold at £1 fell in November and December after peaking in October, according to TNS Worldpanel data.
The £1 price point accounted for 8.5% of all sales by value in the grocery industry in the four weeks ending 1 November.
In the four weeks ending 27 December the most recent period for which figures are available the round pound accounted for 7.1% of sales, a drop of 1.4 percentage points.
However, sales at £1 were still well above the same period a year before, when they were 4.1% of all grocery sales.
TNS director Edward Garner said that retailers had moved away from £1 deals during the key Christmas trading period.
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