New telephone numbers planned for the Sydney CBD will make it harder to link suburbs to certain phone numbers.
The Australian Communications Authority (ACA) has called for public comment on a new series of phone numbers planned for central Sydney, Newcastle, south west Queensland and Rottnest Island in WA.
All the new numbers will still be eight digits.
The numbers for Queensland and Newcastle have not been used before but the numbers slated for Sydney CBD are already used in some suburbs, and those planned for Rottnest Island are used in Perth.
ACA chairman Tony Shaw said allocating numbers starting with 80, 81, 86, 89, 90, 91, 96 and 99 to Sydney CBD subscribers would give the city a 10-year supply of numbers.
"The proposed changes will not affect the cost of a call although they will change the level of geographic information available for numbers in the Sydney CBD and Rottnest Island," he said.
Comments on the numbering plan must be lodged by August 7.