Labor will attack Scott Morrison over the Manus Island riot, but both sides of the political divide are guilty of inhumane policies spanning more than two decades, writes Paula Matthewson.

Voters paying attention to recent events on Manus Island are going to be disappointed by this week's parliamentary session; particularly if they think it will go any way to lessening Australia's inhumane treatment of asylum seekers.

Following Scott Morrison's dance of the euphemisms – conceding but not admitting on the weekend that he told untruths at media conferences following the fatal Manus Island riot – the Labor opposition will latch onto the Immigration Minister having misled the media and Australian people but dance around the morality of what caused the riot in the first place.

Their Question Time tactics and a likely attempt at a censure motion will focus on Morrison's poor briefing, obfuscation and implied incompetence. But there will be little soul-searching over the wisdom of locating a processing centre in a sovereign state that still struggles to control violence and anarchy within its own populace.

Labor's demands for Morrison to be held to account already sound tentative and hollow. That's because they're picking their way through a minefield. Calls for accountability and censure can be tricky manoeuvres when almost everyone shares the blame. And perhaps more than any other contemporary political issue, the events on Manus Island are the product of successive Australian governments' mandatory detention policies, regardless of the party in office.

The Keating Labor government introduced onshore mandatory detention for asylum seekers in 1992, resulting in the first cases of self-harm, riots and escape attempts. The Howard Coalition government upped the ante, introducing offshore processing, establishing detention centres across a troupe of island states and surreally designating some Australian territories as no longer part of the nation for immigration purposes. A processing centre on PNG's Manus Island was established as part of this Pacific Solution.

Labor's Kevin Rudd vowed to dismantle the Pacific Solution, and so he did on the attainment of government in 2007, only to have this taken as a sign by people smugglers that Australia's borders had reopened. The renewed influx of asylum seekers created all manner of difficulties for the Rudd, Gillard and re-ascendant Rudd governments, which over time reintroduced much of the worst elements of Howard's offshore approach.

These extreme actions were taken by parties on both sides of the political divide ostensibly to protect Australia's borders, prevent deaths at sea and destroy the people smugglers' business model. Yet the principal purpose of "stopping the boats" is considerably less honourable: it's to allow politicians to claim kudos for protecting Australians from a threat that doesn't actually exist.

Both sides ruthlessly exploited nascent voter anxiety about asylum seekers into a full-blown paranoia. By framing the issue as one of border protection rather than immigration or human rights the Howard government implicitly encouraged voters to make a connection between asylum seekers, terrorists and the war on terror. It's hard not to conclude that Howard's ill-founded observation about "people like that" throwing their children overboard wasn't similarly confected to demonise asylum seekers.

Then as the events of September 11, 2001 faded, at least in the minds of Australians, voter unease over asylum seekers emerged as a by-product of the industrial relations battle. Having been brought to a state of high concern by both parties claiming the other was putting their job security at risk, voters began to equate asylum seekers as yet another threat to their employment prospects. Neither side has ever attempted to dissuade this misapprehension, with prime minister Gillard even reinforcing it by capitulating to the unions and imposing a limit on the use of 457 visas for skilled foreign workers.

Voter antipathy for asylum seekers has been kept at a fairly vigorous simmer ever since – it's just too electorally valuable to the parties to be let to go off the boil.

Perhaps most shockingly, Kevin Rudd exploited it on his re-election as Labor leader in an attempt to consolidate his Messiah 2.0 status. Erasing from that prodigious brain any memory of his denunciation of the inhumanity that was the Pacific Solution, Rudd unleashed the ultimate deterrent (and hopeful vote-winner) by vowing that no asylum seeker would ever reach Australia and instead would be settled in PNG.

After Rudd's defeat it was no surprise Tony Abbott also embraced this extreme policy, having pinned his electoral legitimacy on "stopping the boats" (shorthand for "not letting those foreign devils steal Australian jobs, crowd our trains or marry our daughters").

If they were so inclined, shock jocks could rightly claim both Labor and the Coalition have bloodied hands after the fatal riot on Manus Island.

Mandatory detention and offshore processing are bipartisan policies. The Manus Island facility was established by the Coalition and reopened by Labor. And it was Labor's policy, since adopted by the Coalition, to deny any asylum seekers settlement in Australia that reportedly sparked the protest and subsequent riot.

This week's parliament will be filled with raised voices, dramatic gestures and righteous calls for Morrison to be held to account. It's likely former Labor immigration ministers will join the fray. Look closely for looks of chagrin or embarrassment on their faces – this may be an indication of the extent to which they also feel accountable for the policies that led to fateful events on Manus Island.

Paula Matthewson is a freelance communications adviser and corporate writer. She tweets and blogs as @Drag0nista. View her full profile here.