Is the unthinkable slowly, but surely, becoming thinkable? Could the Oireachtas at some point move to close down the Moriarty and Mahon tribunals? It's a question that even a few months ago would have seemed ludicrous. For the past 12½ years the tribunals have been politically untouchable – their early track record in uncovering corruption and wrongdoing insulating them from the criticisms about the huge fees to their legal teams and the snail-like pace of proceedings.

But everything has changed in recent weeks. The admission of critical errors by Judge Moriarty and the recent scathing criticism of the Flood/Mahon tribunal by the Supreme Court has changed, probably forever, the climate for tribunals.

It's important to stress that there are no signals from government or the opposition parties of any concrete move to withdraw support from the tribunals and precious few TDs and senators are willing to stick their heads above the parapet to publicly criticise them.

But privately, senior politicians say in the corridors of Leinster House, there is no shortage of whispered discussion about calling time on the tribunals. "It is being discussed tentatively by serious people in politics," one senior, highly respected opposition figure told the Sunday Tribune last week.

He stressed that as things stand there wouldn't be any move by the Oireachtas. But with the costs of the two tribunals building by the day and estimates that their final bill will be between €600m and €1bn, the senior figure said that matters were likely to "reach a tipping point" sooner or later.

The latest figures for the two tribunals show Mahon costing €90m and Moriarty at around €40m. But with many third-party costs to be factored in and both tribunals still conceivably with months and perhaps years to run, there is no shortage of guesstimates that Moriarty will end up costing €250m-plus and the more extensive Mahon inquiry will be a multiple of that.

At some point, that final bill is going to come dropping into a minister for finance's budgetary projections and at a time when the country can ill afford it.

There are other signs, apart from whispered conversations, that the mood music has changed. In the Dáil this week, Enda Kenny will table a number of questions on the Moriarty tribunal, including pointedly asking the Taoiseach the projected additional costs of the tribunal's decision to hold extra public sittings.

Eamon Gilmore has put down a more routine question asking about the costs accruing to the Taoiseach's department arising from the Moriarty tribunal and if any estimate is available of the likely final cost.

Others are prepared to go further than dipping their toe in the water. Senator Jim Walsh of Fianna Fáil, a strong critic of the tribunals, has a long-standing motion before the Seanad calling for the "exorbitant fees" being charged by senior and junior counsel in tribunals to be reduced to €969 and €646 a day respectively – as proposed, but never implemented because of fears of a lawyer exodus, by the government back in 2004. The same motion is to go before this week's meeting of the Fianna Fáil parliamentary party.

Walsh believes the two tribunals should be wound up and any outstanding areas of investigation completed by a newly established commission of inquiry, a much cheaper way of carrying out investigations.

"I don't think we can sit on our hands and do nothing while such outlandish fees are being incurred," Walsh said, adding that this was especially the case at a time when very difficult cuts in spending were being implemented.

"You can't ask people to play their part and on the other hand, we're paying €1m a year [to the tribunal lawyers] for glorified administrative work. That is four times the salary of the Taoiseach. Even if you reduced the pay to the levels [proposed by the government], they would still be paid €350,000-€400,000 a year, which is more than the most skilled hospital consultants.

"I was party to the decision of the Oireachtas to set up the tribunals in 1997. I feel a personal sense of responsibility for the scandalous imposition on taxpayers arising from the legal costs. The terms of reference spoke about dealing with urgent matters of public concern.

"Thirteen years later, it has to be obvious to all of us, they've failed in meeting those terms of reference and as a consequence, we've failed the taxpayer for allowing them to continue. I apologise to the taxpayer and in my opinion everyone in the houses [of the Oireachtas] at that time should apologise. It imposes on us a very strong obligation to effectively address the matter now and put an end to the huge costs," Walsh said.

Billy Timmins, Fine Gael's foreign affairs spokesman, has also attempted to raise the issue of tribunal costs and their duration in the Dáil.

"There is a sense of frustration that the tribunals like [that old saying about] the poor will always be with us," Timmins says, adding that he wants the Taoiseach and the Minister for the Environment – whose departments are responsible for Moriarty and Mahon respectively – to give a statement on where both tribunals stand.

The tribunals' costs are also like to come under further scrutiny of the Dáil's Public Accounts Committee, with chairman Bernard Allen stating that he intends to call figures from the Taoiseach's department to examine if the Moriarty tribunal's costs have been effectively controlled.

The Sunday Tribune has also learned that legal advisers for Fine Gael have been in correspondence with the Moriarty tribunal, challenging the tribunal's interpretation that a cheque for $50,000 given to Fine Gael by Telenor – a shareholder in Esat Digifone – falls within its terms of reference.

The tribunal accepts the cheque was not a payment to Michael Lowry but says that because Lowry was then a trustee of the party and hence a 'connected person', it is covered by the terms of reference.

It is understood this point has been disputed by lawyers for Fine Gael, who say that the specific legislation in this area would only be relevant if Fine Gael was a body corporate and the 'connected person' had a controlling role.

The Taoiseach has also recently written to Judge Moriarty to enquire as to when his report will be complete. Similar letters written to the Moriarty tribunal in the past have had no impact in bringing the tribunal to a conclusion with none of the political parties, for differing reasons, willing to force the issue.

But that was then and this is now – post the Supreme Court's hugely significant judgement on Flood/Mahon (which potentially opens the door for many of those refused costs and accused of obstructing its work by the tribunal to now seek their costs) and the Moriarty tribunal's recent very public difficulties.

The Supreme Court's Adrian Hardiman's judgement – and particularly his comment that the length, complexity, expense of the tribunals, and the readiness in this country to have recourse to them, "is to be deplored" – has been the talk of politicians in the last fortnight.

It's quite clear, one senior opposition party figure said last week, that the current Supreme Court has little tolerance for tribunals.

That is particularly relevant because businessman Owen O'Callaghan currently has a challenge against the Mahon tribunal pending in that very court.

O'Callaghan is arguing that before any final report is published, all affected parties should be issued with preliminary findings, as has been the case with the Moriarty tribunal.

If he wins that case – and the expectation in legal circles is that he will – it could considerably add to the duration of Mahon.

It won't have escaped Judge Mahon's attention that it is now over 18 months since Moriarty issued its first preliminary findings and there is still no sign of a final report. Once preliminary findings are issued, the potential for them to be picked apart is obvious.