Research by the Consumers' Association of Ireland has shown the cost of directory enquiry calls has risen significantly over the last number of years.
The research shows the cost of calls can vary from 60c to €5.58 for a one-second call.
The CAI said it was so difficult to decipher the charges paid by consumers to directory enquiry services it required the help of a mathematician.
The report in its latest Consumer Choice magazine show the costs from an Eircom landline can vary massively.
It said a one-minute call to 11811 costs €3.42, while the 11850 service costs €5.58, and the 11890 service costs €3.40.
However, it said that each service has a set-up fee and a minimum price, which sees consumers being charged €5.58 for a one-second call to the 11850 service.
The CAI said there is no pattern to the charges and they differ hugely depending on the provider, the network and whether the call came from a prepaid or bill pay phone.
Eircom, which operates the 11811 number, said its charges are fully transparent and are indicated during all advertisements and promotions.
11890 Chief Executive Nicola Byrne said it would require a mathematical genius to work out all the different charges.
She called for greater regulation of pricing from the Commission for Communications Regulation.
However, ComReg said it does not regulate pricing but does offer a directory enquiries price comparison guide on its website, callcosts.ie.
The CAI's Dermot Jewell said there is massive profiteering attached to the costs being charged.
Speaking on RTÉ's Morning Ireland, Mr Jewell said it is very difficult for consumers to work out how much they will pay in advance of a call.
He said perhaps Ireland needed to have a discussion with the UK, where the regulator there has directed that the consumer be shown what the service provider is charging and then what the mobile carrier is taking.
