Lord Hague urged EU and UK leaders to “create a better atmosphere” and work through their disagreements over everything from ambassadors to shellfish, but especially tensions over the Northern Ireland Protocol.
It comes amid increasing concern in Government over scenes of sectarian violence in Northern Ireland.
Lord Hague told Times Radio: “We are going to bump along from one crisis to another. And the latest very worrying news from Northern Ireland is really the worst of this.”
He added: “That really is a final warning to get relations onto a better footing because there are talks going on at the moment that are apparently making some progress about the Northern Ireland Protocol. But it shouldn’t have to come to that crisis point to get those talks to make progress.”
Unionist leaders link the violence to loyalist tensions over the Irish Sea border imposed as a result of the UK-EU Brexit deal. The new trading border is the result of the Northern Ireland Protocol, introduced to avoid the need for a hard border on the island of Ireland.
Lord Hague said when Brexiteers made the case for leaving the EU, the suggestion that it could easily create instability Northern Ireland was an “inconvenient detail”
He added: “It is the big flaw actually in Brexit – which in many other ways can work successfully for this country.
“Certainly at the time of the referendum it was kind of brushed aside. Some of us were warning about it at the time.”
However, he said he did not think there was a “lack of focus” from the Government now on the issue, adding: “But there’s this very intractable problem of what you do about the borders of Northern Ireland in Brexit given the determination to keep an open border with the Republic of Ireland and if this issue is not completed and not settled to the satisfaction of the different communities in Northern Ireland.”
Boris Johnson has not ruled out travelling to the province if the disorder continues, according to reports.
The riots started late last month in loyalist strongholds, involving children as young as 12, and have escalated.
Other factors said to have inflamed tensions include the decision not to prosecute leaders of the republican Sinn Féin party for breaching Covid regulations at the funeral of a former IRA intelligence chief last June.