Melbourne train staff gear up for 48-hour strike after 'insulting' pay offer

Melbourne train maintenance workers say they're "miles apart" in pay negotiations with Metro Trains.

The Rail, Tram and Bus Union has asked for a 17 per cent pay rise over four years - the same as the drivers got last year.

Union secretary Luba Grigorovitch says Metro has offered just two per cent over four years.

"The offer that has been made is absolutely insulting," she told reporters on Thursday.

"At the moment we're absolutely miles apart."

The union is preparing for a 48-hour strike after lodging a claim for protected industrial action, which Metro Trains spokeswoman Sammie Black said was a disappointing surprise.

"We have been making good progress in negotiations, had discussions as recently as yesterday when the subject of money was raised for the first time only yesterday," Ms Black said.

Last year Victorians were subjected to rail and tram strikes as the RTBU pushed for new pay deals and better conditions for staff.