Australia's electricity network operators have slammed a federal government proposal to increase the thickness of overhead NBN cables.

In early June the Department of Communications revealed it was proposing to increase the thickness of NBN cables on power poles to 48mm - about the size of a wrist - without requiring local or state planning approval.

Carriers currently have limited immunity under the Telecommunications Act from local, state and territory planning and environmental laws when installing overhead cables with a diameter of 30mm or less.

But the government wants to extend the "low-impact facilities determination (LIFD)" exemptions to cables with a diameter of up to 48mm, among other changes.

NBN had told the government that in some HFC areas it would be necessary to piggy-back additional cables on existing overhead cable bundles.

The rollout of overhead cables has long been a thorny issue with communities due to the visual impact of the changes.

Critics to the government's June discussion paper argued the proposed changes meant cabling could be rolled out against a community's wishes with no option for objection, and ahead of an area's own infrastructure plans.

But in new submissions to the proposal made public this week, pole operators lent their voice to the chorus of dissent, arguing the increase in cable size would result both in safety and cost issues.

Endeavour Energy said the heavier cables were more likely to break a pole if snagged by a passing vehicle.

It also highlighted safety concerns, referring to a 2013 fatality associated with the removal of uninsulated electrical conductors similar to the HFC cables.

"If the [cables] are not properly installed and maintained there could be significant detriment caused to the safety of persons, the integrity of the power poles and the continuity of electrical supply," it argued [pdf].

"The MTM cabling assets now proposed for inclusion as low impact facilities are materially different to the existing fibre optic assets and this needs to be recognised."

West Australia's Office of Energy Safety said [pdf] poles would likely have to be replaced to cope with the heavier cables, at a cost of around $10,000 per pole depending on size, location and configuration.

Ergon Energy [pdf] also argued the necessary pole replacement would incur it "unrecoverable costs", additionally so when considering its commercial arrangement with NBN didn't cover the extra devices that may need to be mounted to its poles.

Fees to companies like Telstra and Optus would also need to rise, according to Ergon, which said it charges based on the 30mm diameter.

It also argued that as the pole operator, community members concerned about the visual impact would complain directly to the company, rather than the NBN - potentially damaging its brand.

Western Power [pdf] agreed stringing a 48mm cable would add to a pole's structural loading and impact asset integrity, resulting in a "measurable loss of useful life for that asset".

"Reductions in useful life will result in Western Power having to bring forward asset replacement," it said.

"Remediation of assets earlier than expected has flow-on cost impacts to electricity network customers."

The Queensland Transport department and Western Australia's Horizon Power also echoed the concerns. The consultation period on the proposal has now ended.