At a time when Theresa May has enough problems keeping her government intact, Ireland may be regarded as an annoyance in British government circles.

The border between Ireland and Northern Ireland is an inconvenience as she attempts the incredible political balancing act of reconciling her cabinet around a deal that might plausibly satisfy the remaining 27 governments of the European Union. The commitment by the British government to uphold the Belfast Good Friday agreement limits the kind of economic model the UK can pursue to just those models that are compatible with having an open land border with the EU on the island of Ireland.

The Chequers proposals are useful, from an Irish perspective, in so far as they represent a unified British position on the future EU-UK relationship that allows negotiations to move forward. However, it also seems clear that this UK position will be subject to further negotiations for months to come, including during the planned transition period, and it is by no means certain the 27 governments will agree to allow access to the single market without the UK paying in or continuing to allow the free movement of workers. The resignations of Boris Johnson, David Davis and other ministers also indicates that May has stretched her cabinet as far as they will go, and it remains to be seen if their newfound unity will survive the inevitable compromises arising from the negotiations to come.

Ireland’s urgent concern is to have a definitive, agreed solution for the Irish border before the UK leaves the EU in March 2019. The details of trade do not need to reach the same level of finality by that stage. And that’s where the border is an irritation, reducing as it does the scope for the UK to walk away from the trade negotiations. That would carry the sizeable political price of reneging on part of the agreement and risk worsening the already unstable politics of Northern Ireland, where the devolved assembly has been out of action for nearly a year and a half.

It is tempting for some British politicians to argue that nothing is agreed until everything is agreed, but it is important to recall that the Good Friday agreement was signed in April 1998 and lodged with the United Nations as a formal treaty. Twenty years of relative peace and enhanced prosperity have followed, and it must surely be understandable that people on the island of Ireland are adamant that the agreement should not be a pawn in the Brexit negotiations, not least because Northern Ireland’s population voted remain.

The UK government committed on 8 December 2017 to “the avoidance of a hard border, including any physical infrastructure or related checks and controls”. Moreover, it also agreed to a backstop agreement, which means that in the absence of any other agreement “the United Kingdom will maintain full alignment with those rules of the internal market and the customs union which, now or in the future, support north-south cooperation, the all-island economy and the protection of the 1998 agreement”.

This solemn commitment must be honoured, and the EU negotiators have made it abundantly clear that until there is a robust solution for the Irish border, there will be no future agreement with the UK on trade.

The June summit of EU heads of government was meant to be the final presentation of the British position on the border, but the statement from Chequers came too late for that.

The October council meeting is the last opportunity for the 27 EU governments to agree on a proposal on the border, which would leave just enough time for them to ratify any agreement made with the national parliaments. As with all such council meetings, it is highly desirable to have everything hammered out in advance so that heads of government simply need to sign off.

In this regard, May has been handed a golden opportunity by the Austrian chancellor, who has called an exceptional summit for 20 September to discuss migration. That creates an opportunity to hold any necessary negotiations on the Irish border with the other 27 governments, so that October’s council meeting can simply sign off on it as planned and can then make greater progress on the future EU-UK trade deal.

Ireland would like to see the UK remaining as close as possible to the EU for trade – or indeed holding another vote in case the British people no longer want to leave – but we won’t pay the political price of a hard border in Ireland to achieve it.

• Brendan Howlin is the leader of the Irish Labour party