Immigration Minister Peter Dutton’s petulant, aggressive, blame-the-media response to being rigorously but fairly questioned by Barrie Cassidy yesterday about the recent armed assault on the Manus Island detention camp is consistent with the man’s political persona. He is thin-skinned and uninterested in debate; it was instructive that he resorted to the Trumpesque justification that he had facts that no one else did when challenged on the colossal discrepancies between his own version of events and that of the local police commander (described by Dutton as “the Twitter version”).

For Dutton, the assault on the camp was all about a local five-year-old boy being lured in by detainees. In that context, Dutton presumably sees those events as more akin to the rescue of a child from the clutches of paedophile asylum seekers than what the local police commander described as a drunken rampage by armed soldiers unrelated to a 10-year old (Dutton seemingly can’t even get basic facts straight) getting fruit from the detention camp a week earlier.

But we’ve been here before, and it isn’t all about Dutton. In February 2014, when Manus Island asylum seeker Reza Barati was murdered trying to hide from a mob during a riot, the Immigration Department and its then-minister Scott Morrison immediately, and without evidence, tried to claim Barati had brought his death on himself by trying to escape. The department’s version of events quickly unravelled, and Morrison had to backtrack. In October 2014, the department accused staff of its contractor Save The Children of encouraging self-harm among detainees — based on a dodgy, biased “intelligence report” — and removed them from Nauru. This claim too unravelled — the department’s own report blowing the claims out of the water was sneaked out after Malcolm Fraser died, in an attempt to hide it — and the department was forced to make two humiliating public apologies and pay more than $1 million in compensation to STC and its staff.

[Of all the things we have taken from asylum seekers, the worst by far is hope]

In 2014, Morrison also dismissed reports of poor medical care, asylum seekers being stripped of medicine and medical equipment and deteriorating mental health among detainees as “sensational claims”, only for those claims — which the Department tried to suppress — to be repeatedly confirmed by the department’s own internal documents. Morrison also claimed that Manus Island asylum seeker Hamid Kehazaei, who died from septicaemia from a simple cut on his leg, had received “outstanding care”. It is now known a lazy Immigration Department public servant didn’t bother checking his emails to see a request for the evacuation of Kehazaei and disputed the advice of doctors when he did, delaying the eventual evacuation that might have saved Kehazaei’s life.

The department and then-minister Morrison also strongly implied they were unaware of claims of widespread sexual assault in the Nauru detention camp, only for that to be revealed as false by a parliamentary inquiry that found evidence the department and Morrison had known about them shortly after the Coalition was elected in 2013.

And Dutton angrily dismissed claims that Greens Senator Sarah Hanson-Young had, back in 2013, been stalked and spied on while on Nauru by the department’s sub-contractor, Wilson Security. The claims, he said, “were completely unfounded”, and Hanson-Young was an “embarrassment” to Australia. That, too, fell apart — Wilson eventually admitted that the stalking and spying had occurred and apologised to the Senator. Dutton never has.

There’s a clear pattern here, whether it’s Dutton or his predecessor Morrison — first comes the lie, then the truth emerges eventually, resisted furiously by the department, extracted by the media, parliamentary inquiries or independent reviews. And the lie is invariably intended to smear: Barati was responsible for his own death; Hanson-Young was an embarrassment; doctors were inventing claims of poor health treatment; asylum seekers and contractors are responsible for self-harm. Now here we are again — in Dutton’s paedophile panic version of events, detainees provoked the assault on their own camp in which a large number of shots were fired into the facility.

[Rundle: destructive civil disobedience is the only answer to most recent Nauru horror]

The claims are not merely intended to smear, they’re intended to distract. The Immigration Department is the least competent agency of any level of government in the country. It can’t run billion-dollar tender processes without major probity, it can’t keep records, it is unable to hold its contractors to account, it can’t provide proper medical services to its prisoners, it can’t keep them safe from sexual and physical assault, random gunfire or even murder, it can’t keep asylum seekers’ information secure, it has been the subject of some of the most scathing audit reports in decades. And then there’s the small matter that it has also overseen the complete “loss of credibility” of one of the economy’s most important immigration programs, the 457 visa program, despite a review and an overhaul in 2014.

It is past time for a major independent inquiry into the many, and massive, failings of this discredited, deceitful department. Ministers may lie and bungle, but ultimately they answer to voters. The Immigration Department has had a series of epic failings. It is high time they were made to answer.