Nearly four out of 10 callers to the new directory enquiry services are being given the wrong number.
Many callers were given the wrong number
A 'mystery shop', undertaken by the industry regulators Oftel and ICSTIS, revealed major failings in service standards across the board.
Directory enquiry services were deregulated in August and have suffered since from bad publicity.
However, the mystery shop of 40 providers found some to be cheaper than the old 192 directory service.
In August, BT's 192 directory enquiry service stopped giving out numbers after 46 years of service.
It was replaced by a range of competing directory enquiry services - all beginning with the digits 118.
With callers now free to choose between 20 rival directory enquiries firms - all with different telephone numbers - some have complained that the new system is confusing.
Oftel and ICSTIS made over 2,000 calls to the new directory enquiry services, in the biggest mystery shop since the switch from 192.
In only 62% of cases were callers given the right telephone number.
When consumers complained, only eight out of ten were offered a refund.
Oftel told BBC News Online that it would like to see all providers offer a refund when a wrong number is given out.
However, industry rules do not oblige providers to offer an automatic refund.
"I hope that this research will act as a spur to individual companies to improve the accuracy of their services," said Paul Whiteing, Deputy Director of ICSTIS - the regulator with responsibility for telephone services.
"Those that don't risk losing their customers to other directory enquiry providers,"
But it was not all bad news for the providers or consumers.
Ninety-five percent of calls were answered, and some of the new 118 services were found to be far cheaper than 192.
The cheapest call to a directory enquiry service from a BT land line was just 23p, down from 192's standard charge of 40p.
Nevertheless, the Consumers' Association, which recently undertook its own mystery shop of the 118 directory enquiry services, said providers needed to improve fast.
"We welcomed liberalisation of the market but many of the new services are not performing to the right standards and are failing customers," a Consumers' Association spokesperson told BBC News Online.