Better stock up on your favourites! Price of chocolate could rise by a third by Christmas Rising cost of cocoa butter will push every 100g of milk chocolate up 21p Other crucial ingredients such as milk powder are also more expensive Bad weather has hit key growing region of Ivory Coast, experts explain We all look forward to a few extra little luxuries at Christmas. But this year, your favourite festive treats could hit your wallet as hard as your waistline, with the cost of chocolate set to soar by up to a third. Crippling rises in the price of cocoa butter could add 21p to the cost of every 100g of milk chocolate by December, experts said. Totting up: Rising prices of cocoa butter will push up your average 100g sweet bite by 21p this December It would affect everything from truffles to advent calendars and chocolate coins. The cost of producing chocolate has gone up by 33 per cent in the last year thanks to a 70 per cent rise in the price of cocoa butter, a 50 per cent rise in milk powder prices and a 15 per cent increase in whey powder costs. Cocoa powder and sugar have fallen in price, but they account for a much smaller proportion of production costs, according to the report for trade journal The Grocer. So far, chocolate makers have sheltered consumers from some of the costs. There has been a small 7.5 per cent rise in the price of a Cadbury's Dairy Milk bar, while a box of Quality Street costs 14.3 per cent more. It could have an impact on all chocolatey treats - from brownies to truffles; advent calendars to coins But with peak season approaching, there may be price hikes to come ahead of the Christmas rush. Cocoa butter makes up around a quarter of the production cost of milk chocolate, said analysts Mintec. Prices are currently at a four-year high of £4,000 a tonne, a 70 per cent increase on this time last year. Bad weather has hit the key growing region of Ivory Coast, leading to a lower supply and a poor forecast for the 2013/14 crop, while demand is unusually high. Mintec analyst Liliana Gonzalez said: "Rising cocoa butter prices and inflation on other key ingredients have taken their toll on chocolate manufacturers." Upmarket maker Thorntons has put prices up by an average 11.5 per cent in the last 12 months, said The Grocer. But in contrast, the price of a box of Celebrations is currently the same as this time last year, while a box of Roses costs only 1.3 per cent more.