Ofcom has set out new rules demanding clearer information for customers on how much it will cost them to call 0870 numbers, but has stopped short of requiring a price cut.

Under the new rules, phone networks will be made responsible for ensuring that customers know how much they will be charged for calling an 0870 number. They will not be allowed to describe the numbers as 'national rate' unless the price is in line with that for calling a 01, 02 or 03 number.

The new rules, which come into effect in August 2009, follow a consultation by Ofcom, which found that consumers were often confused over the cost of calling 0870 numbers. Companies that do not comply with the new rules could be subject to fines.

According to research by price comparison website Moneysupermarket two thirds of people who call 08 numbers from a mobile phone have no idea how much they are being charged.

Ofcom said it and Payphoneplus, the organisation that regulates phone-paid services in the UK, had received " many complaints" from people calling these numbers in the past few years but was unable to provide an exact figure.

"We’ve put these rules in place following a consultation last year, which found customers are often confused about how much they are charged by their mobile and land line company for calling these numbers. We hope these new rules will help protect consumers and clear up confusion," said a representative.