Australian Prime Minister Scott Morrison is facing renewed criticism after sharing bushfire-themed party campaign ads that opponents have condemned as "disgusting" and a respected defence association said was "milking" the crisis.

Facing sustained anger for his handling of the months-long crisis, Mr Morrison sought to get on the front today, announcing increased military assistance to beleaguered volunteer firefighters.

In a string of media appearances, he vowed every resource would be provided to help ease a disaster that has killed 23 people and burned swathes of the country, announcing more funding for water-bombing planes and the call up of 3,000 reservists.

But he found himself in fresh scandal after tweeting a video heralding his announcements about the military, and his Liberal Party made a similar post linking to the party website.

The non-partisan Australia Defence Association, a public-interest watchdog, said the Liberal Party advert was a "clear breach" of conventions keeping the military out of politics and accused the party of "milking ADF support to civil agencies fighting bushfires".

There was more fervent criticism from Mr Morrison's political opponents for his tweet that promised "more Defence Force boots on the ground, more planes in the sky, more ships to sea, and more trucks to roll in to support the bushfire fighting effort".

It was accompanied by a military-themed video that was "authorised by S. Morrison, Liberal Party, Canberra."

We're putting more Defence Force boots on the ground, more planes in the sky, more ships to sea, and more trucks to roll in to support the bushfire fighting effort and recovery as part of our co-ordinated response to these terrible #bushfires pic.twitter.com/UiOeYB2jnv — Scott Morrison (@ScottMorrisonMP) January 4, 2020

Opposition spokesman for international development Pat Conroy accused Mr Morrison of trying to "exploit a national tragedy" and described the ad as a "new low".

"To then solicit donations to the Liberal Party while millions of Aussies are giving to fire appeals is beyond belief. Note this disgusting ad was personally authorised by this scum of a PM," he tweeted.

Labor Senator Murray Watt also took to Twitter to demand Mr Morrison "show some respect to fire victims, the fireys (firefighters), the ADF, and the people facing fire fronts right now. Take down this Liberal Party ad. Now".

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Mr Morrison was earlier forced to cut short a Hawaii holiday following a barrage of criticism for vacationing while exhausted volunteer firefighters battled blazes across the country and millions of people in Sydney choked on toxic smoke.

Criticism of his absence was widespread, sparking street protests and a flood of angry social media posts demanding #whereisscomo.

He returned and promptly visited bushfire-hit communities where he was heckled by residents and criticised by a party ally.

A tearful pregnant woman and a volunteer firefighter refused to shake his hand and other residents peppered him with verbal abuse and suggested, colourfully, that he leave.

"People in these situations have a mix of emotions," Mr Morrison said playing down the interactions and stressing he had been welcomed elsewhere.

"These arms have given a lot of hugs," he said.

