While Malcolm Turnbull’s clever tactic to regain control of the political agenda via a threat to call a double dissolution election won plaudits from the commentariat, it has wrecked what was left of the credibility of his Treasurer, Scott Morrison. Turnbull’s shocking treatment of his most senior minister raises serious questions not merely about the relationship between Prime Minister and Treasurer but who exactly is running economic policy.

Morrison has had a troubled time in Treasury, where — perhaps unrealistically, given the demands of the portfolio — he was expected to shine after the poor performance of Joe Hockey. Whatever you think of the idea of increasing the GST, Morrison ran hard on the idea and devoted considerable effort to negotiating with state premiers on the issue, although he never accepted that a GST rise might actually be used to fill the health and education funding gap created by Tony Abbott and Hockey in 2014. But with Labor running hard on a GST scare campaign, Morrison was pulled up sharply by Turnbull in February when a GST rise was taken off the table. The Treasurer then had to deliver what turned out to be a very difficult Press Club address in which he said nothing except to explain the abandonment of the GST rise and why the government had made no progress (in fact it has gone backwards) on the return to surplus. The media, including friendly forces like those at 2GB, caned him.

Turnbull then rinsed and repeated that treatment on negative gearing, with Morrison making the running on capping what he described as the “excesses” of negative gearing before that too was shut down by Turnbull under backbench pressure to enable a clearer campaign against Labor’s own negative gearing reform proposal. And that campaign blew up in Morrison’s face as well after he relied on a BIS Shrapnel report to attack Labor before the firm admitted it wasn’t based on Labor’s policy.

Amid reports of tension between Prime Minister and Treasurer, the idea of bringing the budget forward a week to accommodate a ploy for a double dissolution election began to circulate, until Morrison quashed speculation two weeks ago and then again last week, repeatedly saying the budget would be on its scheduled date of May 10. It was a statement Morrison kept on making right up until yesterday morning — right up until his Prime Minister announced it would be on May 3. Last night on 7.30, Turnbull declined to soften the blow, dismissing Leigh Sales’ suggestion he might have consulted with Morrison on the timing of the Treasurer’s major economic setpiece of the year.

Indeed, according to Morrison’s own version of events, another cabinet minister knew that the budget had been moved before he, the Treasurer, knew. He told journalists yesterday “I was advised this morning that it will be on May 3” at a cabinet teleconference at 10am. But Attorney-General George Brandis had written to the Governor-General a letter about Turnbull’s request to prorogue Parliament that was received at Yarralumla at 9.15am, so Brandis knew at least 45 minutes before Morrison of the Prime Minister’s plans.

Turnbull and Brandis then let Morrison make a fool of himself a few minutes later when he insisted to Ray Hadley that the Budget would be on May 10. Brandis, of course, would not have prepared correspondence to the Governor-General by himself – senior staff at the Attorney-General’s Department would also have known before the Treasurer.

Then there’s the role of the head of PM&C, Martin Parkinson, who would have been at the centre of Turnbull’s plan to recall Parliament. Parkinson, too, was apparently party to keeping Morrison in the dark, as well as the PM&C staff who would also have known before Morrison. Parkinson, of course, is the former head of Treasury and could have advised Turnbull quite accurately as to the logistics of bring the budget forward a week without consulting with the current head of Treasury, John Fraser. But to make matters worse, in February Parkinson was put in charge of the tax reform process by Turnbull, in effect sidelining both Fraser and Morrison. So PM&C now runs tax reform and brought the budget forward without — at least according to Morrison’s own version of events — informing Treasury or the Treasurer.

And remember that Parkinson is ably supported at PM&C by his former Treasury deputy, David Gruen, whose warehousing in PM&C for perceived thoughtcrime by Abbott has made 1 National Circuit into a rather convenient mini-Treasury for Turnbull.

And given Parkinson and Gruen are overseeing tax reform, what is the role of Morrison and Treasury in the budget anyway? The budget is supposed to be the Treasurer’s moment to shine. It’s his document, his forecasts, his fiscal strategy. But not the 2016 budget — that is now Turnbull’s document, to be delivered by Morrison, with the key fiscal reform plan prepared by Parkinson, and the timing decided by Turnbull.

It’s hard to recall a Treasurer who has ever been treated similarly, with such an evident lack of interest or consultation. And funny how no one is talking about Scott Morrison as a future leader at the moment, isn’t it?