European leaders may be preparing to recognise a united Ireland, in a declaration that would pave the way for the north to swiftly rejoin the European Union. At their first Brexit summit on Saturday, the EU’s 27 leaders are expected to discuss a text stating that if Ireland unified, the north would automatically become part of the EU.

The inclusion of the text is a victory for the Irish government, which had pressed for the inclusion of a “GDR clause”, a reference to the integration of the former east German state into the European Community after the fall of the Berlin wall. The declaration is bound to raise fears that Brexit could trigger the unravelling of the UK, although there is no majority in Northern Ireland for unification.



EU diplomats are braced for a fierce reaction from the UK, given the angry tabloid headlines that followed speculation about the status of Gibraltar. After lobbying from Madrid, the EU agreed that the Spanish government would be able to exclude the Rock from any EU-UK trade agreement if it was not satisfied with the status of the territory.



The Irish clause is informed by the Good Friday peace agreement, which states that north and south of Ireland have a right to unify if a majority agree north of the border. Enda Kenny, the taoiseach, has argued that it is important for the north of Ireland to have “ease of access” to rejoin the EU if reunification were to occur.



A draft of the summit minutes seen by the Guardian refers to the Good Friday provision for a united Ireland and adds that this event would bring the north into the EU. The draft says: “The European Council acknowledges that, in accordance with international law, the entire territory of such a united Ireland would thus be part of the European Union [in the event of Irish unification].”

Brexit has put the issue of a united Ireland back into the spotlight, but public support remains cool. In Northern Ireland, a recent poll found that a clear majority of 62% would vote for the territory to remain in the UK, while only 22% backed a united Ireland. Voters in the republic are also sceptical, especially if reunification comes with a price tag.



Enda Kenny has argued that it is important for Northern Ireland to have ‘ease of access’ to rejoin the EU in the event of reunification. Photograph: Michael Kooren/Reuters

Asked how they would vote in a referendum if the cost of a united Ireland was €9bn a year, only a third of Irish respondents said they would vote yes, while a third would vote against and the rest were undecided.

The GDR clause is contained in a text separate from the EU’s official negotiating guidelines, because it is seen as a reflection of the Good Friday agreement, rather than an issue to be negotiated with the UK.



Brussels insiders are expecting a short summit on Saturday where EU leaders swiftly put their seal to the Brexit negotiating guidelines, a document outlining the EU’s red lines, which have already been agreed at a technical level.



However Owen Paterson, former Northern Ireland secretary and Conservative MP, warned the EU against any action over Irish unity : “The UK voted democratically to leave the EU last year and it would be quite inappropriate for the EU to meddle with the integrity of the UK during negotiations and very unwise, given the current position in Northern Ireland.

“It is really quite out of court and very unhelpful. Genuinely really unwise. There is no threat to the peace process but if they are going to do this, given the strength of feeling about a border poll, it would be really unwise.”

As the clock ticks down to the launch of formal negotiations after the 8 June election, there are signs that the EU is becoming increasingly exasperated with the UK. On Thursday, Angela Merkel said British politicians were living under the illusion that the UK would retain most of its EU privileges once it leaves the bloc.



Shortly before giving this speech to the Bundestag, the German chancellor spoke to the European commission president, Jean-Claude Juncker. He reported on a dinner the previous night at No 10 Downing Street, where he and the EU’s chief Brexit negotiator met Theresa May and her top officials.



One EU diplomat said: “I am deeply pessimistic that there will be a positive outcome from this negotiation,” putting the chances of the UK crashing out of the EU without a deal as higher than 50%.



The EU is frustrated that May’s team has not, as they see it, “engaged with reality” on David Cameron’s promises to pay into the EU budget until 2020 – a promise Brussels insists the British must stick to. “They [the British] are not just on a different planet, they are in a different galaxy,” said the source.