Unions have told the ABC that Telstra's copper network is in a state of disrepair, with workers at the coalface of the infrastructure using plastic bags to protect cables from water.

The telecommunications pits have been nicknamed 'bag-dad' by contractors because of the plastic bags, that are in theory supposed to keep the water out.

The copper network is a crucial element of the Opposition's alternative broadband plan.

But Shane Murphy, the assistant secretary of CEPU's New South Wales branch, says as far as he is concerned, there is no other option than to replace the ageing copper wires.

"Unless we do it, customers around western Sydney and across Australia will have poor internet and phone services for many many years ahead," he said.

Key points: Unions say Telstra's copper network is in a state of "disrepair".

Unions say Telstra's copper network is in a state of "disrepair". Unions have nicknamed the cables ‘bag-dad’ because of the plastic bags used to protect them.

Unions have nicknamed the cables ‘bag-dad’ because of the plastic bags used to protect them. CEPU NSW assistant secretary Shane Murphy says it is time to replace the whole network.

CEPU NSW assistant secretary Shane Murphy says it is time to replace the whole network. Telstra says it spends hundreds of millions of dollars a year operating and maintaining its copper network.

Telstra says it spends hundreds of millions of dollars a year operating and maintaining its copper network. The Coalition has vowed to replace any copper that does not meet minimum standards.

"There is no bandaid solution to this - whether it's in Sydney, Perth, Melbourne, Adelaide, country towns - plastic bags and ringbarked cables are everywhere.

"It's time to replace the whole network, not a part of it."

The Government's NBN plan will almost completely replace the copper and deliver services over a new optic cable right to the home.

The Coalition wants to run fibre-to-street hubs and then use the existing copper wires for the final link.

The Opposition says its plan will be cheaper and delivered faster.

Telstra says it spends hundreds of millions of dollars a year operating and maintaining its copper network.

"The copper's been going well for 100 years, I think it'll keep going for another 100," chief David Thodey said.

In regards to plastic bag fixes, the company says it does use plastic to waterproof certain areas in a small amount of cases.

"In the vast majority of cases, we will do a permanent repair, but sometimes to get a service up and running faster for a customer, we do a temporary repair," a company statement said.

"In a small number of cases this may involve using plastic to waterproof the area, but it is only ever a temporary measure.

"Our policy is to replace temporary fixes with more robust, permanent solutions as quickly as possible."

NBN plans compared Fixed line speeds 100mbps (1000mbps in future) 25-100mbps Satellite speeds 12mpbs-25mbps 12mpbs-25mbps Fibre to home 93% of premises 22% of premises Fibre to node 0% of premises 71% of premises Finished by 2021 2019 Cost $44 billion $29.5 billion Read our explainer on the network differences

Mr Murphy says quick fixes have contributed significantly to the state of the network today.

"Piecework is where people are paid per job instead of per hour and this is where people are quickly moving to the job, getting it done as quick as possible without any checks on quality," he said.

"In our view that has exaggerated the problem of what we've got here today."

'Network not being maintained to support services'

The ABC consulted the expert opinion of independent engineer Peter Hitchiner.

Mr Hitchiner is chair of the Information, Telecommunications and Electronic Engineering College Board of Engineers Australia.

"When water gets on to copper cables, particularly on the joints, it will cause degradation to the performance of the cable," he said.

"It's not designed to have water on it and they're tested in an effectively dry environment."

The ABC then showed Mr Hitchiner photographs of the cables.

"Clearly the enclosure's been removed from there and the cables are exposed, and if that has simply had a plastic bag put over it it's not going to protect the infrastructure from damage, from water, and it's going to impact the delivery of services," he said.

"It does not appear from those photographs that the network is being maintained in a way that would be able to support the services that it should be able to support."

The Coalition has vowed to replace any copper that does not meet minimum standards.

But communications spokesman Malcolm Turnbull does not know exactly how much that will cost.

"You don't really know until you actually get in there and see what is there," he said.

"This is one of the reasons, one of the reasons why there've been so many problems with the rollout and the cost of the rollout."

NBN Co is expected to give an update on the rollout and whether it has met its financial year targets in the next few weeks.