Major-General (ret) Jim Molan, speaking to Fairfax Media from the Middle East, said the ships were a ''terrific capability'' and had to be ready on schedule.

The Canberra was formally named at a special ceremony in Melbourne on Friday. Work on Adelaide's hull is still under way in Spain.

With a combined price tag of about $3 billion dollars, the two vessels will each need a crew of 358 navy, army and air force personnel and will be capable of carrying more than 1000 soldiers and their equipment. HMAS Canberra is expected to be commissioned into the Australian Defence Force next year.

Tens of billions of dollars have been slashed from forward defence spending estimates since work on the Landing Helicopter Docks (LHD) began in 2008.

General Molan conceded the ships had come in for some criticism (due to their sheer size) and that there were concerns about finding crew and training soldiers to deploy on board them.

''But you can overcome issues such as crewing and training as long as you have the willpower to do it,'' he said. ''They (the LHDs) are a big step up but it is one that is within the reach of the ADF.''

While other figures in the military, including former chief of army Lieutenant General Peter Leahy, have supported the capability not everybody is an enthusiast.

Andrew Davies, a senior analyst with the Australian Strategic Policy Institute, said ''if I was setting out to design an amphibious force for Australia it wouldn't involve ships that are this big''.

''(But) I would possibly include a much faster vehicle like the Jervis Bay.''

The Jervis Bay was a high speed catamaran ferry commissioned in the ADF during the Timor intervention.

He said it was ''extremely unlikely'' the LHDs would ever be used for the job they were designed to carry out - amphibious assaults.