Anywhere else in the world, a man holding high office who has been as discredited over his expenses as Ceann Comhairle John O'Donoghue would have to resign because his actions would be regarded as tarnishing the respected position he holds.

Here, O'Donoghue's colleagues, such as Fianna Fáil backbencher Noel O'Flynn, seriously try to argue that respect for the office of Ceann Comhairle means we should back off with our criticism of the vast expenses claimed by the man.

It's a nonsense. Brian Cowen knows it is a nonsense. The opposition knows it is a nonsense. Except for one or two TDs living on Planet Denial, our elected representatives know it is a nonsense. The public knows it is a nonsense. And as if people aren't angry enough, the failure to clean up the expense regime of the political classes is pushing the national mood to a point where reasonable debate is impossible because nobody believes a word out of politicians' mouths any more.

If our political leaders believe that the revelations about John O'Donoghue's publicly-funded lifestyle are only about one man with greedy spending habits and an overblown sense of entitlement, then we well and truly deserve the mess we are in.

They are not. The Sunday Tribune and reporter Ken Foxe have not led the investigation into the former minister's expenses claims in the Department of Arts Tourism and Sport as an idle curiosity or some sort of vindictive campaign.

We are doing it because they provide a window into the kind of indulgence and excess that have permeated our political system in as insidious and dangerous a fashion as the lack of governance in banking destroyed our financial system. It undermines politics in the same way as the Fás scandal continues to undermine the credibility of directors of state agencies who oversee their spending on behalf of the public.

John O'Donoghue has chosen neither to defend the payments nor to fall on his sword. Worse still, he refuses to comment by hiding behind his position as Ceann Comhairle, arguing he must be "beyond politics".

This course of action, especially as it remains unchallenged by the taoiseach and senior colleagues, is damaging the government's ability to get its message across about Nama, public spending cuts, public sector pay cuts and tax rises.

Today, we publish further details of O'Donoghue's expenses released under the Freedom of Information Act, this time for his years as Minister for Arts, Tourism and Sport from 2002 to 2005.

They reveal that, far from being a habit he grew into, his preference for expensive trips abroad with his wife was indulged in from the off. Within eight days of taking up his appointment on 6 June 2002, the minister and his wife Kate-Ann were off to Korea for the World Cup, where Roy Keane's spat with Mick McCarthy left any chance of flying the flag for Ireland in tatters. The total cost of flights for that trip was €11,441, with more than €4,500 in hotel bills for the minister, his wife and two officials.

After this, the pattern we have grown used to emerges: first-class flights, limousine hire (with especially large bills once again cropping up for the Cheltenham festival) and liberal use of the government jet.

Limousine hire for three church services – the funeral of Lady Beit and the memorial services for Iraq victims Ken Bigley and Margaret Hassan – came to €2,371.10, not counting the use of the government jet to get to Liverpool and London for two of the ceremonies. O'Donoghoue's total expenses for three years from 2002 to 2005 are €174,447. This does not include his use of the government jet 10 times.

Unlike the information released to the Sunday Tribune under FOI for his period as minister in 2006 and 2007, very little detail has been supplied. It does not include expenses paid for by boards (and ultimately the taxpayer) such as Tourism Ireland, Horse Racing Ireland and the Irish Film Board for travel and accommodation in the United States, France, Britain and elsewhere. For some reason, it does not include accommodation costs on many of these trips.

O'Donoghue also has questions to answer about why his wife accompanied him on official business, not just to far-flung destinations, but to routine EU sports or culture ministerial meetings in Brussels, Hungary and Italy. But O'Donoghue, as usual, has declined to comment.

He can either justify these expenses or he cannot. He either has something to hide, or he has not. But at the moment, the retention of John O'Donoghue as Ceann Comhairle is as damaging to the reputation of the body politic as the revelation that Bishop Eamon Casey had a son was to the church.

We do not, even in good times, like our politicians acting with an arrogance and hubris that is totally at odds with their avowed dedication to service.

The same goes for the Fás directors, many of whom enjoyed the fruits of the poor governance they were responsible for policing at the state training agency. There have been calls for their resignation. For some reason, Mary Coughlan, as minister for enterprise, says she would accept their resignations "if they offered them". She should stop pussyfooting around and demand them.

The Rody Molloy saga, in which Brian Cowen first backed the discredited Fás director and then accepted his resignation, did neither the taoiseach nor Molloy any favours. Both men looked weak. Better these things are done quickly than through some kind of "humane" code.

The problem, as we know all too well, is that there is no culture of accountability. Last week, the Greens showed they have some political clout in government by insisting on the resignation of all directors who sat on the boards of banks whose distressed loans will be taken over by Nama as part of the toxic loan legislation. John Gormley talked straight when he called for the heads of the Fás directors too.

It's not pretty; it's not easy when it concerns colleagues and friends. But facing up to excess in the political hierarchy is one of the first steps that must be taken if politicians are to regain any credibility. Is Brian Cowen really ready to sacrifice public support for fiscal reform on the altar of grandiose limousine bills for the Cheltenham festival? The symbolism is that raw.

If the opinion polls run true to course, half of Fianna Fáil TDs will lose their seats and the cabinet will be out of a job. Brian Cowen would be the first to say that he respected the will of the people on election day. But one Fianna Fáil politician will remain, of course. And that is the Ceann Comhairle, John O'Donoghue, because the biggest perk of his job is that he is automatically re-elected to the Dáil.