The $270 million project, which started in July 2010, will extend the Metro network to Sunbury.

It was originally expected to be completed by the middle of this year.

At last week's Hume Council meeting, Cr Jack Ogilvie said he had heard reports the project was going to be delayed.

"I was told by a pretty reliable source that it will be held up and won't be ready for at least a year," Cr Ogilvie later told the Weekly.

"It's to do with electrical cabling [being] all in the one channel, which has caused a lot of problems and has to be redone."

But Transport Department spokeswoman Kellie Routledge quashed the delay claim and said the project was still scheduled to be completed this year. However, she could not give a specific date.

"The majority of civil works for the Sunbury electrification project are nearly complete," she said.

"As part of the project's quality assurance process, there has been some rectification of construction issues with the installation of underground conduits along the rail line.

"Rectification works are not unusual on large-scale infrastructure projects and these issues are now addressed."

Ms Routledge said a date for the start of the new train services had not been set.

"The exact date for metropolitan services starting from Sunbury will be determined as part of the detailed timetable service planning by Metro and will be announced closer to completion of the project."

While work continues on the Sunbury project, work on the upgrade of Diggers Rest station is almost complete.

Ms Routledge said the refurbished station was expected to reopen next month.

"Works are continuing at the station to finalise footpaths and station building construction works, as well as prepare for landscaping in the precinct."

She said while the station was closed, the new 550-space car park was open.

Ms Routledge said many people were unaware that the car park was open, with hundreds of spaces still vacant each day.