DUBLIN — Ireland has loudly proclaimed its unity with rest of the EU since Britain voted to leave the bloc, but a clash over the Irish low-tax regime could shatter the cohesion.

In Irish business circles, Brexit has triggered a brainstorm on how best to use it as an opportunity to push back on the EU's crackdown on Irish tax policy.

Their nuclear option: "Irexit."

It doesn't trip off the tongue like the British version, but the theory goes that any EU encroachment on the low corporate tax rates that have underwritten Ireland's economic transformation in recent decades could undermine its unmatched enthusiasm for the EU and amplify what are, for now, a tiny minority of voices calling for an Irish exit from the European Union.

For the government in Dublin, Brexit already poses huge problems, such as the reemergence of a border with Northern Ireland that could destabilize the Good Friday peace accord, and the threat to Irish business sectors that are heavily reliant on trade with the U.K.

The U.K.’s decision to leave the EU and the election of the staunchly Europhile Emmanuel Macron as French president have combined to reestablish France and Germany as twin engines for the bloc. The Franco-German duo are keen to rewrite the economic rules of the eurozone, possibly targeting one of Ireland's touchiest subjects: its bargain-basement corporate taxes.

Without openly invoking the threat of an Irish exit, the business community spies an opportunity to shove the EU in the opposite direction. Business lobbying group IBEC is urging Dublin and the European Commission to relax spending rules to allow investment on infrastructure and for exemptions from EU state aid rules to support Irish businesses hit by Brexit.

“This is going to be very hard fought,” said Fergal O'Brien, IBEC's director of policy and public affairs. “There’s real money at stake."

Dublin is currently fighting a European Commission ruling that its tax treatment of U.S. tech giant Apple was generous to the point of illegal state aid. The decision prompted the center-right Fine Gael-led government to strike a rare Euroskeptic note: It accused the Commission of interfering with Irish sovereignty.

Some observers, however, saw the decision as an indication that the EU's patience with Ireland on tax may have run out.

Within weeks of the Apple decision, the Commission reanimated an old tax reform plan: a move to adopt the so-called common consolidated corporate tax base (CCCTB). Defeated by the U.K. and Ireland in its last iteration in 2011, the reform package aims to prevent tax avoidance and allow company profits to be taxed according to where the revenue is earned.

Meanwhile, the emergence of Macron, whose electoral program accused Apple and Ireland of “distorting competition” in Europe, has bolstered French confidence in pushing for a different fiscal vision for the EU now that the U.K. is leaving.

His new finance and economy minister, Bruno Le Maire, says France aims to agree on a common tax policy with Germany in 2018 to form the basis of “harmonization” of tax rates across the eurozone within five years. Ireland’s finance ministry declined to comment on the plans.

No backdoor changes

The EU does not currently have the power to control national tax rates, and any change to this would require a unanimous vote by all members. The CCCTB plan is seen as a plot to change this through the backdoor — and Dublin is adamant that it will not pass.

IBEC's O'Brien says the CCCTB plan could threaten half of Ireland’s corporate tax base.

Furthermore, he argues, "if we see a U.K. outside the EU without EU state aid constraints, that’s going to be a big challenge for Ireland. You could see very sharp direct competition.”

"I think there will be a further move toward a German-French axis [in the EU], and that is something that we are very uncomfortable with" — Retired diplomat Ray Bassett

The main political parties are unanimous in their defense of the corporate tax policy as a non-negotiable mainstay of Ireland's economic transformation since the 1950s. According to this view, lower taxes are required to make up for the insurmountable weaknesses of Ireland’s peripheral position geographically and its tiny domestic market.

Even during the bailout years in the wake of the global financial crisis, when the International Monetary Fund, European Central Bank and Commission oversaw Irish finances, Dublin managed to cling on to its 12.5 percent rate.

Today, as a sign of commitment to its low tax policy, the Irish government is completely opposed to accepting the €13 billion in back taxes, plus interest, that European Commissioner for Competition Margrethe Vestager ordered Apple to pay Ireland last August.

Ireland has appealed against the ruling in lockstep with Apple in the General Court of the European Union, with the Irish public's backing: A poll by the Irish Times and Ipsos Mori at the time found a majority of the austerity-weary population supported the government’s decision to appeal.

They knew exactly what they would be giving up. The amount Vestager said Apple owed Ireland was nearly as much as Ireland's entire health budget for 2017, which was €14.6 billion.

“Our taxation policy has been the same now for more than 40 years. We will not be changing it. It’s straightforward,” said Dara Murphy, a European People’s Party vice president and former Irish European affairs minister. “It’s a matter for Ireland.”

Tough sell

Despite all the sound and the fury, Irexit remains a tough sell for now.

Unlike the U.K., Ireland doesn't have a wealthy past to look back to prior to the EU, having transformed from one of Europe's poorest countries into one of its richest during its time in the bloc.

Leaving would mean abandoning the euro and facing the repayment of Ireland's outsize debt in its new, presumably devalued, currency. It would face a return to the heavy trade dependence on the U.K. that characterized its economy up to the 1970s.

And irrespective of tax rates, multinationals like Facebook and Google would presumably not retain their European headquarters in a nation of 4.6 million that was no longer part of the single market.

The most recent Eurobarometer poll, published this month, rated Ireland the most positive country in the EU, with 77 percent of Irish people surveyed expressing optimism about the future of the bloc, and overwhelming majorities in favor of the euro, single market and immigration from the EU. It showed no evidence that Irish support for EU membership has been affected by the U.K. decision to leave the bloc.

Ray Bassett, a retired diplomat who has become a high-profile critic of the Irish government's approach to Brexit, is one of the lone voices advocating that the implications of Brexit are such that Ireland should consider matching it.

“The European Union is changing and without the British as allies I think there will be a further move toward a German-French axis, and that is something that we are very uncomfortable with,” Bassett told POLITICO.

His polemic on Irexit for right-wing U.K. think tank Policy Exchange was received with such enthusiasm by Brexiteers that it prompted a series of rebuttals in the Irish media, with Prime Minister Leo Varadkar saying the EU “is a common European home that we helped to build and we’re going to stay where we belong, at the heart of it.”

Be less prescriptive

Irexit's only champions in parliament are a handful of radical-left politicians for whom it's not a priority issue. The most Euro-critical large party, Sinn Féin, supports Ireland's EU membership and is campaigning for special status for Northern Ireland to allow it to stay in the bloc.

All told, it would be a leap to conclude that opposition to the European Commission's corporation tax proposals could give rise to an Irish desire to end EU membership itself.

Commission representatives, for their part, refused to get dragged into the debate. Instead, the EU’s executive arm pointed to an impact assessment that it conducted as part of the CCCTB proposal.

The assessment included an analysis on how CCCTB would change the tax receipts of each EU country. For Ireland, that analysis showed a drop of -0.14 percent in its corporate tax receipts and a largely budget-neutral effect as a whole.

No doubt, Ireland lost a key ally on shaping the EU’s corporate tax policy when the U.K. voted to leave.

But Conor O’Brien, a senior tax partner at KPMG, is among those arguing that Brexit has actually given Ireland additional arguments with which to defend its corporate tax rate.

“One is, given Ireland is under more economic pressure now as a result of its biggest trading partner leaving the EU, the low corporation tax is important,” he said. "The other is, perhaps the EU should be a little bit less prescriptive with countries because the EU imposing its will is perhaps why Britain left."

Bjarke Smith-Meyer contributed reporting.