Mr Banks let rip in devastating fashion not seen since his return to Parliament as Act's sole MP last November after a 12-year absence.
He slammed the largely symbolic measure for leaving the "nasty aftertaste of Green xenophobia".
Having only moments earlier described Russel Norman, the Brisbane born-and-raised Greens co-leader, as an "Australian interloper" , Mr Banks might be accused of suffering the same affliction.
Coming on top of Monday's equally acid put-down of the Electoral Commission, you could only draw one conclusion from these savage critiques.
The old Banks is back. The three months under the cloud of a police investigation into the complaint about donations to his Auckland mayoralty campaign and whether he filed a false return inevitably took their toll. But that experience has hardened Mr Banks to again handle what he categorises as the "toxic" nature of Parliament.
Much of the opprobrium was deserved. There may not have been grounds for prosecution, but there was a problem of perception over his contacts with internet millionaire Kim Dotcom and casino operator SkyCity.
Mr Banks' pretence otherwise made it more of a problem. His deaf-and-dumb routine on TV One's Q+A was truly bizarre - as was his now immortal statement about "not having come up the river in a cabbage boat".
But even the most cold-hearted politician would have winced at the fate he suffered in the House one evening. Normally, a victim of ridicule can leave if he or she cannot stomach it.
As the responsible minister for a Bill which had reached its committee stages, Mr Banks was required to stay in the House. He was trapped. Labour MPs rounded on him mercilessly.
In obvious reference to the incident, Mr Banks said the debating chamber was a "very lonely place for the lone traveller".
No doubt the thought he might still be alone for another three years after the next election was another ingredient fuelling the invective directed at the Electoral Commission. He could hardly have hardly been surprised the commission advocated the scrapping of the so-called "coat-tailing" provision as part of its Government-ordered review of MMP. This rule means parties which win an electorate seat are automatically exempted from having to reach the 5% threshold for the party vote and can bring extra MPs into Parliament in proportion to their lower party vote.
Act has benefited mightily from what has long been considered an anomaly in the electoral system. Rodney Hide's victory in Epsom in 2005 left National with little option but to do a deal in the seat with Act in 2008 or watch the latter party's votes go to waste. Act delivered in 2008 with four such extra MPs. Last year, Act failed to deliver. Now, what would otherwise be a rock-solid National seat is all that stands between Act and oblivion outside Parliament.
Removal of the coat-tailing provision would effectively end Act's utility for National. But National, as the governing party, has to decide whether or not to write the legislation that pulls the trigger.
Staring down the same abyss, United Future's Peter Dunne has been guarded about what National should do. Not so Mr Banks. He has sought to discredit the commission as being incompetent, while accusing the quasi-independent body of succumbing to submissions from Labour and the Greens who sought to gerrymander the system in their favour.
Mr Banks then further upped the ante by predicting National would not have the political will to "gas" its two most reliable and effective partners.
He is right in one respect. It would send a dreadful message about the long-term value of major-minor party relationships in coalition arrangements. On the other hand, National will look both self-serving and disrespectful of the commission if it does not pick up the recommendations.
One option might be to delay the Government's response to the commission's findings so they cannot be implemented in time for the 2014 election. An only slightly more credible alternative would be to shift the implementation date for any changes to the electoral system beyond the next election on the grounds parties need more time to adjust. Both scenarios would leave National open to the criticism it is gerrymandering by not acting speedily on the recommendations of the commission it tasked with remedying those components of the system the public dislikes.
Another possible way of easing National's dilemma would be to ignore the commission's call for the "overhang" to be abolished.
Sticking with the status quo could see Mr Banks' and Mr Dunne's two votes being retained for the centre-right without National losing a seat, which is what would have happened if the current Parliament had been capped at 120.
The benefit might be marginal to National, but it is likely to be operating on even thinner margins at the 2014 election than last time when it comes to retaining power. The trouble is, that option does little to help Act or United Future.
The decision might ultimately come down to National assessing whether there is any point in providing safe harbour for Act or United Future any longer and stand candidates in their seats with the intention of winning them.
Mr Banks sees his job as two-fold: ensuring Epsom is Fortress Act while refocusing the party's message to appeal to what Act sees as an untapped market of hundreds and thousands of owners of small to medium businesses.
This audience is seen as sympathetic to the Act product - highlighted by what the party sees as its "breakthrough" policy of charter schools. The question is whether Mr Banks as Act's messenger, having suffered more knockdowns in his political career than Lazarus, can rise once more.
• John Armstrong is The New Zealand Herald political correspondent.
