Chocolate production costs are rising - but fierce pricing activity means shoppers are paying less for their Christmas chocs than they were a year ago.

Deals such as Morrisons’ recent 2-for-£7 offer have made the average price of a tin or tub of key wrapped chocolate brands - Quality Street, Roses, Celebrations and Heroes - just £4.91 in the big four in the past three months. A year ago, they were selling at an average of £5.15 during the same period.

Although some brands have followed the recent festive trend of getting smaller as commodity prices rise (Celebrations tubs weigh in at 750g this year compared with 855g a year ago, and Heroes have dropped to 780g from 800g), the price drops are not simply down to tinkering with tub weights: the average volume price of Christmas chocs has also fallen.

On a per-kilogram basis, chocolate tins and tubs are costing shoppers £6.14 this year compared with £6.20 12 months ago. The average kilo price of Mondelez’s Heroes has fallen 3% year on year, although the volume price of Mars’ Celebrations has risen by 9%.

Chocolate tins and tubs have long been fiercely competitive lines for the supermarkets, but data reveals deep price cuts on such products are coming earlier than in previous years.

Three or four years ago, some retailers were still selling tins and tubs at full price (about £10) in September and October. As a result, in 2011 the average price of such products was considerably higher at this time of year - with the average unit price of tubs coming in at £5.83, and the average kilo price at £6.71.

This year, however, not one of the big four was selling tins or tubs at more than £5, according to data. Tesco ran a promotion that temporarily dropped the price of some of its tubs to £4 in mid-September, and this month Morrisons in effect took the price of some lines down to £3.50 with its 2-for-£7 offer. During the Morrisons promotion, Asda dropped the price of all four branded tins and tubs to £4 for a limited period.

While it is still early in the season - and it remains to be seen whether retailers will continue to offer such deep cuts - the lower prices will be an early Christmas gift to shoppers spooked by news that the cost of producing the average milk chocolate bar has soared over the past 12 months due to inflation on key ingredients such as cocoa butter.

For retailers and suppliers, however, these key Christmas lines - even this early in the festive season - are making precious little margin.