Jeremy Corbyn has restated his support for the reunification of Northern Ireland and the Republic, as he heads to Belfast for his first official visit.
The Labour leader’s spokesman said he believes most people across the island want the countries brought back together, adding that any change must happen through consent and that Mr Corbyn is committed to the Good Friday Agreement.
But the comments will raise eyebrows across the Irish sea where the Labour leader is due to give a speech on Thursday morning, setting out his approach to post-Brexit customs and the Irish border.
It also comes as Labour is at odds with its Northern Irish sister party, the SDLP, which has warned that Mr Corbyn’s current approach to Brexit will not prevent a hard border being redrawn with the Republic.
Mr Corbyn is a prominent and long-time supporter of the unification of Ireland and his views have sometimes placed him at odds with official party policy.
Pressed on Mr Corbyn’s opinions on reunification, his official spokesman said: “Over the years he has made his position clear that the majority of those people across the whole island of Ireland wanted to see that outcome, a united Ireland.
“But in the context of the Good Friday Agreement that can only come about through that constitutional process that is laid down in the agreement and Jeremy fully supports that.”
Under the terms of the Good Friday Agreement, a united Ireland will only occur with the majority consent of people in Northern Ireland and the Republic of Ireland.
In 1984, a decade before the first IRA ceasefire, Mr Corbyn met with Sinn Fein leader Gerry Adams in London and, a year later, he opposed the Anglo-Irish Agreement saying it strengthened rather than weakened the border.
Mr Corbyn’s spokesman said that during his visit to Belfast he would seek to “engage with all communities and people across Northern Ireland” on both the peace process and Brexit.
Following the comments, Downing Street was quick to highlight that Theresa May “has been absolutely clear about her commitment to the Union on a number of occasions”.
In his speech at Queen’s University Belfast, marking 20 years since the referendums which endorsed the Good Friday Agreement, Mr Corbyn will call for the revival of power sharing at Stormont.
To help end the deadlock, Mr Corbyn will call on the UK government to reconvene the British-Irish Intergovernmental Conference, which the Good Friday Agreement provides for.
He will declare that “Labour will not support any Brexit deal that includes a return to a hard border on this island.”
The leader will then argue that Labour’s proposed new “comprehensive UK-EU customs union, with a British say on future trade deals and arrangements, coupled with a new, strong relationship with the single market would prevent communities being divided”.
But the SDLP has already written to all Labour MPs urging them to defy Mr Corbyn’s will and back a plan to stay in the single market, saying it is the only way to avoid a hard border.
Labour’s current position is that it “respects” the 2016 referendum, that Britain’s EU membership must end, that the country should remain outside the single market as it stands.
But in her letter, Ms Hanna wrote: “It is important to note that customs union membership alone will not prevent [an Irish] border.”
She wrote ahead of a vote in the Commons expected in coming weeks on a plan to keep the UK in the European Economic Area, effectively meaning it would stay in the single market – which Mr Corbyn is refusing to back.
Ms Hanna added: “[A hard border] will only be prevented if we retain full access and full alignment with the single market and customs union. No other solution is possible.