It is lauded near universally as a highlight of modern British statecraft that has saved countless lives — but Brexit has unleashed a swath of attacks on the landmark agreement that brought peace to Northern Ireland.

With the Irish border question a major Brexit stumbling block, some prominent Leavers see the Good Friday Agreement — which will pass its 20th anniversary in April — as a barrier to the type of U.K. exit that they desire. That has led to an unprecedented public broadside against the peace deal from the Brexit wing of British politics.

In the space of barely 24 hours, former Northern Ireland Secretary Owen Paterson and Labour Leaver Kate Hoey declared the deal had "outlived its use." Conservative MEP Daniel Hannan said the agreement had "failed."

Leading backbench Brexiteer Jacob Rees-Mogg made a more subtle argument: attacking the premise that Brexit puts the agreement in jeopardy. "It would be wrong to pretend that the [Northern Irish] border forestalls Brexit and we would not expect the prime minister or the Cabinet to fall for such a weak argument. It is only put forward by people who have always opposed Brexit," he wrote in the Telegraph.

“It will advertise to the EU27 that making any binding treaty or international agreement with the U.K. is a hazardous enterprise" — Brendan O’Leary, an architect of the Good Friday Agreement

Coordinated or not, this barrage against a key pillar of the peace process brought an angry reaction from Dublin. Irish Deputy Prime Minister Simon Coveney — whose government is a co-signatory of the 1998 accord that has been exported to societies trying to move out of violent conflict from Sri Lanka to Colombia — accused Brexiteers of "reckless" gambling with the peace process.

The timing of the attacks has raised eyebrows, too. Northern Ireland has been without a devolved government for over a year, and talks to restore power-sharing broke down last week in Belfast. And while there is currently little prospect of a return to the violence that cost more 3,000 lives during Northern Ireland’s 30-year-long "Troubles," it is a sensitive political moment.

The breakdown in talks in Northern Ireland has raised the possibility of direct rule from London, by a Conservative government propped up by Democratic Unionist Party MPs. According to Brendan O’Leary, professor of political science at the University of Pennsylvania and one of the architects of the agreement, that would violate the Good Friday deal and even prompt the EU to think twice about signing a Brexit pact with the U.K.

“It will advertise to the EU27 that making any binding treaty or international agreement with the U.K. is a hazardous enterprise because its sovereign parliament, backed by its supreme court, reserves the right to modify or abolish every such agreement by routine legislation,” said O’Leary.

Almost 90 percent of Tory Leave voters say destabilizing the peace process is a price worth paying for Brexit. But opposition among some Brexiteers to the Good Friday Agreement runs deeper than their fears that it could scupper dreams of a clean break with Brussels. A number of prominent Tories are long-running critics of an agreement (brokered under a Labour government) that paved the way for former IRA fighters to enter government. Environment Secretary Michael Gove has even compared the process that led to the 1998 deal to the appeasement of the Nazis in the 1930s and the condoning of the desires of pedophiles.

Prime Minister Theresa May’s reliance on the Democratic Unionist Party to prop up her government is another factor. Although the DUP shared power with Sinn Féin for more than a decade, the party opposed the agreement and hard-liners, including some of its Westminster MPs, have called for its reappraisal.

DUP Brexit spokesperson Sammy Wilson told POLITICO that Hoey and Paterson’s comments had “been badly interpreted” and in his view "had nothing to do with Brexit at all." Wilson said that opponents of Brexit “were abusing the agreement to keep the U.K. in the European Union.” He also accused the Irish government of failing to understand Northern Ireland.

“[Irish Prime Minister Leo] Varadkar and Coveney are naïve and inexperienced, they don’t really understand the situation in Northern Ireland except from a very narrow, southern perspective,” he said.

Wilson said the structures of the agreement that require the largest nationalist and unionist parties to share power “needed to be looked at again,” but he accepted that changes are unlikely with cross-party support for the agreement in the House of Commons.

Sovereignty issues

The Good Friday Agreement is an international treaty between the U.K. and Ireland. Under the deal, everyone born in Northern Ireland can claim Irish or British citizenship, or both. The agreement also allows Northern Ireland to leave the U.K. and join the Irish republic in the event of a majority vote.

Writing in the Evening Standard, Matthew O’Toole, a former adviser to David Cameron, suggested that the role afforded to Dublin in Northern Irish affairs explains “why hard Brexiteers have set their sights" on the deal.

"U.K. sovereignty is, in one corner of the realm, qualified by the rights of one group of citizens and by another EU member state that has a say in the administration of that region," he wrote. That doesn't square with the Brexiteers' overriding desire to take back control.

This broad political support will likely protect the agreement, but that leaves an Irish border issue that so far defies a simple solution.

Others see grave risks in the attacks. Duncan Morrow, a former head of the Community Relations Council in Belfast, said Brexit risks undermining the Good Friday Agreement’s most significant achievement — turning Britain and Ireland into “genuine partners, not enemies.”

“Brexit puts all of this at risk, because it is framed as putting up barriers, moving away from common values and rules and ending common membership of a shared project,” he said.

Beyond the DUP, nationalist and unionist politicians in Northern Ireland warned against the dangers of "talking down" the agreement.

"Imperfect as our dispensation is, there is no other way to accommodate difference, respect diversity and deliver government for all our people," said Colum Eastwood, leader of the nationalist Social Democratic and Labour Party.

This broad political support will likely protect the agreement, but that leaves an Irish border issue that so far defies a simple solution.