ARE the Greens, the party that views sustainable energy as a core value, getting windy? For two years now, the junior coalition partner has stood shoulder to shoulder with Fianna Fáil as the two parties have implemented some of the toughest measures ever introduced by a government ? taking all the flak and the poor opinion polls with admirable resolve and stoicism.

But last week's intervention by Senator Dan Boyle – clearly with the leadership's stamp of approval – calling for a quicker wind-down of Anglo Irish Bank seemed, temporarily at least, to open up a potentially serious policy chasm between Fianna Fáil and the Greens.

The fact that it came after a week in which the party had been mauled in the overblown controversy about taxing commercial vehicles, and the day after Green leader John Gormley was unfairly lacerated in some Sunday newspapers, raised suspicions that the party was feeling the heat and reacting accordingly.

Boyle's intervention seemed to confirm the recent suspicion among some experienced hands in the Dáil that the Greens were getting fed up with being a public punchbag and that, some time in the coming months, they would look for an issue over which to walk out of government on a matter of principle.

However, it is an assessment that is strongly resisted within the Greens, and also in Fianna Fáil. Both sides caution against reading too much in Boyle's comments.

"If you listen to what Dan was saying [about the wind-down of Anglo Irish Bank], he was saying let's 'get it approved and do it as soon as possible, while still mindful to ensuring the lowest possible cost to the taxpayer'. He got bounced into the five years [time frame]," one Fianna Fáil figure said, adding that this was no different to what the cabinet believed.

Green sources say Boyle was putting down a marker on behalf of the party that it was concerned about what was happening at Anglo and there was a need to "stop throwing good money after bad".

"It was a question of emphasis. There wasn't a split [between the two parties]. There might have been a bit of tetchiness [between the Greens and the department of finance] but it's already passed," one senior source said.

That seems to be borne out by the statement from the government, following Wednesday's cabinet meeting, that it was "united in its determination in relation to the resolution of the Anglo Irish Bank issue: that it must be done at the least practicable cost to the taxpayer and in a way that gives finality".

The lack of any mention of timescale does suggest, however, that the department of finance view – that setting a deadline of five years or so for winding down the bank is not practical – held sway. It was never going to be any other way.

But at least the Greens had been setting the agenda, unlike the previous week when they never got off the back foot in the furore over motor tax on commercial vehicles.

Party figures also dismiss the notion that, after getting it in the neck for the past two years and struggling in the opinion polls, the Greens are shaping up to pull out of government.

"We're there for the long haul. As long as we're achieving and delivering Green policies, we're there," is the uniform response from Green figures.

They also point out that it would be very hard to find a suitably important issue on which to withdraw credibly from government, and that history tells us that once an election campaign begins, the issue that prompted the election is often quickly forgotten.

One issue that would be important enough for the Greens to take a stand on is the commitment to a ban on corporate donations. Along with the Dublin mayoral election and the noise bill, it's one of several Green measures that the party wants implemented over the next six months or so.

"It's a key issue," Green senator Mark Deary acknowledged. "But I would much rather we achieved that significant reform than make it into a false moral issue on which to go the country. We are extremely anxious to use this period to achieve policy gains."

Fianna Fáil is dismissive of the potential for divisions over a ban on corporate donations.

"It's in the programme for government. It's coming. It'll happen. There may be a bit of butting of heads about the timing of it but that's it," one source said.

The extent of the cuts likely in the forthcoming budget means tensions between the two government parties can't be ruled out. The Greens won't want to see any more cuts in basic social welfare. They might also be uncomfortable at the prospect of the tax net being spread to include the 50% of workers who currently pay no tax.

The Greens may jibe at the perception that the government is hitting the less well-off to fill a budgetary hole. They will also strongly resist flat-rate charges for water or services, although the difficulty in making savings of €3bn means that will surely be on the table.

However, while it won't be easy, the smart money says the government will just about manage to agree a budget and get it through the Dáil.

The real test will come in the New Year when the Greens' insistence on the holding of the Dublin mayoral contest will surely make it impossible for the government to resist calls to hold the three by-elections as well. With the government almost certain to lose all three, the Dáil arithmetic will become extremely tight and will greatly increase the prospect of the government simply running out of numbers, precipitating a general election.

Green Party figures are under no illusions about how difficult that election will be for the party, with only former leader Trevor Sargent holding anything close to a safe seat. They admit that the ferocity of the criticism of the party has been demoralising, particularly as the Greens played no part in creating the economic and banking crises.

Senator Mark Deary points out that, despite last week's hullabaloo, the only change to the car tax regime the party has overseen is allowing people to pay as little as €104 a year – a tax he himself pays for driving a 1.5-litre diesel car.

But, while there is frustration that the party has not got credit for this and other legislation, such as the planning bill and the civil partnership bill, the Greens point to the experience and practical streak of those involved in the parliamentary party and say they can and will roll with the punches.

"They've all served on party councils for long periods. They're no wide-eyed innocents. They are intensely practical," one source close to the leadership said.

And they also take comfort from the experience of other European countries, where the Greens have taken the blows while in government but subsequently bounced back, showing – they say – that Green politics "will persist as an idea" regardless of electoral setbacks.

Such self-confidence will certainly be needed. Since it came into the coalition, the party has been willing to stand over tough budgetary medicine and concentrated on seeking to implement the Green part of the programme for government. Even its fiercest critics would have to admit the Greens have put paid to the myth that they are too flaky to be in government. But there is no question that their resolve and determination to stay there will be sorely tested in the coming months.