Bagged snack and biscuit prices are set to soar by inflation-busting levels over the next month, as another major supplier feels the bite of rising commodity costs.

United Biscuits increased trade price rises this week, with snacks such as Hula Hoops increasing by 4%-5%, while biscuits - including Family Circle - have been pushed up 10%-12%.

The full effect is expected to be felt in stores in the coming months.

UB commercial manager Nick Stuart said that, as well as rising wheat prices, the flooding earlier this year had hit potato suppliers across the country.

Kellogg's has also increased prices across its brands, partly as a result of commodity costs, but would not confirm by how much they had risen.

"Commodity costs continue to be challenging," said a Kellogg's spokeswoman. "We have allowed for the effect of commodity costs in this year's pricing, but can't speculate about possible future plans."

The news comes after wheat prices pushed up the cost of bread last month, with Premier Foods' Hovis brand increasing in price from 96p to £1.04 in Tesco.

Meanwhile, it has been claimed that manufacturers have helped push up the price of food commodities by stockpiling raw ingredients.

The latest Purchasing Managers Index survey, produced by NTC Economics, found that prices paid for raw materials used in food and drink production had risen at their fastest rate since 1998.

This was partly because EU-based food manufacturers had purchased safety stocks of wheat and cereals after global grain harvests suffered from poor weather.

"The rate of growth of stocks bought by food and drink manufacturers in recent months has been exceeded only once in the past 10 years, by a spike in purchasing caused by fears of the millennium bug," said Chris Williamson, NTC Economics' chief economist.