It is a problem which has for generations caused rows among sweet-toothed families when the Christmas chocolates are passed around.

And now consumer body Which? has established that some boxes of festive chocolates really do contain fewer of our favourites, in what could even be a cynical ploy to get us to buy bigger packs.

There is bad news for Quality Street fans as Which? found tins contain half the "ideal" ratio of the most popular favourites, the Purple One and the Green one, explaining why many families scramble over them every year.

Respectively there are only five and six in an average 720g tub, but with people's favourites taken into account there should really be 11 and 10 o fthe sweets, Which? calculated.

The chronic shortage of Purple Ones can be explained by Nestle's selection process, it can be revealed, as it balances out the flavours in tubs by categorizing chocolates into three types, each of which make up one third of the total.

The types are: fruit cremes, chocolates and caramel/fudge. The Purple One falls into the category with tby far the most sweets, the "caramel/fudge" type, which also includes the Caramel Swirl, Fudge, Toffee Penny, Coconut Eclair, Toffee Deluxe, Toffee Finger.