Peak consumer groups have put forth a joint complaint with the communications watchdog over mobile phone companies that charge a per-minute rate for calls to free numbers and the cost of local calls on landlines.

The groups claim that mobile phone calls to numbers such as those of government agencies, telecommunication and utility providers are being charged, with some of the calls costing as much as $7.

Landline calls to 1800 numbers do not cost anything. Calls to 1300 numbers, on the other hand, costs as much as a local call.

A united front consisting of the Australian Communications Consumer Action Network (ACCAN), the Australian Council of Social Service (ACOSS) and the Australian Financial Counselling and Credit Reform Association (AFCCRA) have filed a so-called "super-complaint" on the issue. The complaint has been lodged to the Australian Communications and Media Authority (ACMA), with the regulator being asked to respond within 90 days.

"There is tremendous confusion among consumers as to how much these calls actually cost, because people wrongly assume that all calls to 1800 numbers are free," said Teresa Corbin, acting chief executive of ACCAN.

The peak body, which represents telecommunication companies, said that the ACMA is already looking into the issue as part of an investigation into telephone numbering.

In a statement, the Australian Mobile Telecommunications Association, said that the group "fully supports" the investigation and was co-operating with ACMA.

"The mobile telecommunications industry takes its responsibilities seriously and understands the importance of access issues," said a spokesman for the group.

The groups have forwarded recommendations with their complaint such as changing the billing processes of telecommunication companies or the introduction of a new number range exclusively for mobiles.