By Janine Perrett 

It was Bill Shorten's Crocodile Dundee moment.

He might as well have taunted Malcolm Turnbull with "you call that a budget, I'll show you a budget".

Or more to the point a fiscally conservative, fair budget is what the Opposition claimed last night.

So now we really have a fight.

Not content with setting the policy agenda on everything from super changes to corporate regulation to smoking taxes, the Labor party is now upping the ante on fiscal rectitude.

As I noted yesterday, the biggest disappointment in the Morrison budget was not the cuts to spending but the fact it was all ploughed back into minor tax relief for the middle class; it allowed Labor to claim it was unfair and the actual amount was so miniscule for taxpayers it seemed hardly worth the pain.

The $4 billion plus it will cost the budget bottom line is not miniscule and would have made a start in actually cutting the deficit.

International ratings agency Moody’s was quick to note this point.

Incredibly the Bill Shorten proposal with its $70 billion in further cuts over 10 years should be more to their liking.

If they believe it. But then they didn't believe all the Morrison figures either.

Whereas once the government could raise doubts about the decade long projections, not after yesterday's debacle where the PM and the Treasurer could not explain their own long range numbers.

(This is expected to be remedied today with figures from Treasury, but a bit late and damage was done).

And showing that the world has indeed turned upside down it is Labor that is fighting the prospect of retrospective tax, which the Coalition would introduce under the new superannuation cap.

Do not underestimate how much staunch Liberals loathe the word "retrospective".

Some never forgave the Fraser Government for introducing retrospective tax in the Bottom Of The Harbour tax legislation over 30 years ago.

So hear we have a Labor Government playing a Liberal theme on deficit cutting and blocking retrospective tax while appealing to their own heartland with motherhood bills like enshrining Medicare.

It's not all bouquets for Mr Shorten though; the move to deny medium businesses a tax cut does not stimulate demand and will be unpopular.

Big business will be in a bind though given how they have called for serious debt and deficit repair and did not see anything significant in this budget.

And at least they get a tax cut under the Coalition, even if it takes a decade. That still seems to be sooner than they will get anything from Labor.

There were certainly some simple saves in the Shorten plan, $160 million on the same sex marriage plebiscite and the major cost saving of $6 billion in the vocational sector might be enormous but given the rorting and mess both parties have made of the sector in recent years, means something needs to be done.

There is plenty more that will come under attack in the Oppositions' incredibly ambitious, some might claim fanciful, budget proposal.

But it is shaping up to be an interesting contest for the next eight weeks.