AUSTRALIA Post has been slammed for a postcode gaffe that Deputy Mayor Paul Tully says could cost lives and will cause misdirected mail en masse.

The controversy relates to Australia Post giving postcode 4124 to a development estate in Greenbank and New Beith, known colloquially as "Spring Mountain", when Spring Mountain has been a suburb of Ipswich for decades and is set to be home to thousands of residents in the eastern suburbs.

Cr Tully said Spring Mountain in Ipswich, adjacent to Springfield Lakes, should have a postcode of 4300 - the postcode for most of Ipswich's eastern suburbs.

He said the area called Spring Mountain by locals in Logan was actually in the suburbs of New Beith and Greenbank.

"It is a real estate-developer name and has never been an official place name recognised by the government," Cr Tully said.

"Australia Post never allocates an official postcode to estate names, only to official suburb and locality names.

"This is the first departure from that policy ever in Australia since postcodes were introduced 50 years ago in 1967.

"The Spring Mountain debacle is a monumental stuff-up by Australia Post.

"Because of the two competing postcodes, mail will be held up, misdirected or returned to sender.

"Triple 0 calls to emergency services could be delayed as operators try to work out the scene of a fire or accident. Lives could be lost with delays in identifying if an incident is in Ipswich or Logan."

Cr Tully said this was "a community disaster waiting to happen after some fool in Australia Post assigned a postcode to a non-existent place in Logan City".

"Australia Post has a duty to immediately withdraw the 4124 postcode for Spring Mountain and urgently advise all local residents of New Beith and Greenbank what their correct suburb name is," he said.

Australia Post has not admitted to any error, but a spokesperson did respond to Cr Tully's statements.

"Postcodes are assigned to facilitate the efficient processing and delivery of mail, and correspond with the delivery centres from which mail is delivered," the spokesperson said.

"Local councils define the boundaries of the localities they administer, and we then assign postcodes to those localities based solely on the needs of the delivery network. The housing estate locally known as 'Spring Mountain Estate' is officially gazetted in the locality of Greenbank 4124.

"In some instances a number of locations/suburbs share the same postcode; as is the case with Greenbank and Spring Mountain sharing the postcode 4124. To ensure mail is sorted effectively and efficiently, we encourage residents of 'Spring Mountain Estate' tp use the correct suburb of Greenbank as their address."

Cr Tully said suburb and locality names in Queensland were "approved solely by the state government, not local councils".