Workers and their union representatives say issues with the depth of the cables might prevent the network receiving the independent approvals it needs before trams can start moving passengers on the 12-kilometre track between Gungahlin and the city centre.

But a Transport Canberra and City Services spokesman says the ACT government directorate "fully expects" the project to achieve certification against all relevant Australian standards.

Photos of electrical conduits in a pit near the intersection of the Federal Highway and Flemington Road appear to show some cables installed just a few millimetres below ground level.

This is despite the Australian standard the directorate says will be adopted for the light rail project requiring cables installed underground in areas accessible to the public be buried at least 750 millimetres below ground level.

The pit has been filled in with concrete since the photos were taken, but the Transport Canberra and City Services spokesman said the government understood works at the intersection were still subject to completion and verification checks.

An electrician working on the light rail project, who did not want to be identified because he feared for his job, said he had several concerns about the standard of the work, including the depth of electrical cables.

"There are high-voltage cables that are somewhere between extremely shallow and not very shallow," he said.

"It's not being constructed to standard."

In 2016, the ACT government awarded the Canberra Metro consortium a contract to build and operate stage one of the light rail project.

John Holland, a construction company that is part of the consortium, is responsible for design, construction, operations and maintenance.

The construction of light rail stage one is budgeted at $707 million, but the total cost including operations is $939 million.

Electrical Trades Union ACT officer Mick Koppie said the photos were evidence of a major problem for the ACT government.

He said he had been "getting calls from everyone" about the standard of the work, with several union members working on the project telling him of their concerns.

"I don't think there's any doubt [that the work doesn't comply with Australian standards]," Mr Koppie said.

"Clearly, [the cables] are nowhere near the depth they're supposed to be and in some instances they come very close to the surface."

Mr Koppie said if the work did not receive the third-party electrical accreditations it needed to become operational, Canberrans would be left with "a pretty big lame duck, or white elephant".

"Things need to be repaired," Mr Koppie said.

"I would say we're better off erring on the side of caution and get everything fixed up before we get one passenger on that tram.

"That's going to leave egg on the government's face, but this wasn't their making. It was the builder who did this.

"You've got to be safe rather than sorry, don't you? It would be best to get everything done properly first. I don't know the full extent of what that entails. The experts are telling me a lot of millions to fix it."

Mr Koppie also expressed concern some pits containing high-voltage cables filled up "like a swimming pool" and needed to be drained whenever it rained.

"It's not healthy at all," he said.

A Canberra Metro spokesman said "effectively all" of the electrical cabling for stage one of the light rail project had been installed, but some works, including those shown in the photos taken at the intersection of the Federal Highway and Flemington Road, were yet to be finalised.

"All electrical cabling works on the Canberra light rail project will be checked and verified for compliance by Canberra Metro through their quality management system and through independent verifications," the spokesman said.

A Transport Canberra and City Services spokesman said the project required various third-party accreditations before operations could commence, including certification of electrical works.

"Prior to operations commencing the light rail system will be required to have all necessary authorisations in respect electrical infrastructure, including certification that cable depths at the Federal/Flemington intersection are appropriate," the spokesman said.

"In a project of this size and complexity it is not unusual that there may be various construction matters which require further consideration prior to final sign-off.

"That is why the projects contract and regulatory framework exists."

The spokesman said it was clear significant progress was being made on the project and works would continue through January.

He said trams were still expected to start taking passengers in early 2019, but the exact date was subject to third-party accreditations.

"Transport Canberra fully expects the project will achieve certification against all relevant Australian Standards," the spokesman said.