Melbourne commuters could face lengthy delays if rail workers go through with a strike threat in the next four to six weeks.

The threats come after rail staff rejected a two per cent pay rise over four years and lodged an application for protected industrial action through the Rail, Tram and Bus Union (RBTU).

Infrastructure staff (including track-workers, signallers and administration staff) were pushing for a 17 per cent pay rise, arguing they were the “backbone” of the transport industry.

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RTBU secretary Luba Grigorovitch called the salary offer from Metro Trains “insulting and unacceptable” saying they had “no choice but to take industrial action” if a “fair and reasonable” agreement was not tabled in the next few weeks.

“Our members are not willing to entertain this any longer,” she said.

“Their agreement expired nine months ago and the offer that Metro put forward was terrible: a 2 per cent wage increase over four years and a number of conditions stripped away.”

Despite the threat, Victorian Public Transport Minister Jacinta Allan said Metro Trains had advised the government a strike was unlikely to go ahead.

“The best way to get these matters resolved is through negotiations in good faith and that’s certainly what the Government is urging on both parties,” she told media.

In September 2015, the Melbourne transport system was thrown into disarray when train drivers walked off the job for four hour periods on consecutive days before a pay deal was reached.

The Melbourne CBD was eerily quiet as thousands of city workers pulled sickies or worked from home to avoid the predicted congestion.

– with ABC