At least 28 major defence projects are a cumulative century behind schedule and 18 are over budget.

The projects include Hunter class frigates, battlefield airlifters, patrol boats, the battlefield command system, a series of satellite communications projects and the P-8A Poseidon aircraft.

Marles said it would be a “real challenge” to rein in blowouts, with defence a “significant offender” for placing strain on the budget.

“We’ve inherited a complete mess from the former government,” he told ABC radio.

“When it came to the actual delivery of projects, they were one of the worst governments that we’ve seen in defence procurement history.”

When asked if the government would scrap the troubled French Taipan army helicopters in favour of the US Black Hawk, Marles said he would not comment before the finalisation of a review under way.

Marles said the culture needed to change from the top down to get projects back on track.

At least $6.5 billion of project variations outside of the budget have also been identified.

Treasurer Jim Chalmers and Marles will reveal budget pressures facing the defence department on Monday.

The government says a large proportion of the overspending is because of exchange rates and indexation but also blamed the former coalition government for “chaotic administration”.

“The former coalition government’s investment in defence saw key defence projects blow out in both cost and time – money being flushed down the toilet,” Marles said.

He said the government would deliver on its defence commitments by establishing an independent office to hold projects accountable.

Monthly reports on projects of concern and interest will also be handed to the defence minister directly.

The government will also allocate extra resources to troubled projects to help get them off the ground.

The government pledges to maintain its commitment to spending at least two per cent of GDP on defence.

Expenditure is set to increase to more than $80 billion by 2032.