SPECIALIST fire trucks worth millions of dollars are sitting idle two years after they were brought in to service regional towns.

The latest delay has been blamed on cracks found in some of the five aerial pumpers' booms, with overseas engineers called on to fix the safety problem.

The fault will be covered by warranty, so should not increase costs to taxpayers who have paid about $750,000 per vehicle.

The delay has angered the firefighters' union, which wants the trucks to boost capability in rural areas.

The CFA says the delay is frustrating, but rejects union and State Opposition claims that staffing issues or budget woes have added to the lengthy delay.

But one senior firefighter said the aerial pumpers, which have a crane-like boom that enables them to fight fires in high buildings, were badly needed and the delays were unacceptable.

The firefighter said growing areas such as Warrnambool and Mildura were promised the new hi-tech trucks years ago, and the issue must be resolved quickly.

Opposition emergency services spokeswoman Jacinta Allan has also hit out, blaming budget cuts.

"These tankers were earmarked to undertake specific fire and rescue support for communities right across rural and regional Victoria," she said.

"Victoria's firefighters deserve better from the Liberal National Government as they put themselves in harm's way every day to protect Victorians."

A CFA spokesman released a statement on the issue, saying that the "Aerial Pumper is a new hi-tech appliance that's never been used before".

"Before CFA can put the truck into service, a significant amount of training and testing of the vehicle needs to be done," the spokesman said.

"During the lengthy commission process for the truck, a warranty issue was discovered and CFA is working with the manufacturer to have this fixed."

The CFA said it would continue to work with the union to get the trucks commissioned and hoped to have the new system operating in "a few months".

Read more on the Herald Sun.