Support for a united Ireland has not advanced one step in the quarter century since Northern Ireland’s peace agreement, the leader of the DUP has insisted.

However, Gavin Robinson said unionists could not be complacent about the maintenance of the Union, as he acknowledged the need to convince the growing number of non-aligned middle ground voters in Northern Ireland of the case for the constitutional status quo.

In a pre-election interview with the PA news agency, Mr Robinson also dismissed suggestions his party has recently performed a U-turn on its endorsement of the UK Government deal on post-Brexit trade barriers that in January persuaded the DUP to drop its two-year protest blockade on powersharing at Stormont and return to devolution.

Countering the accusations of flip-flopping levelled by political rivals, he argued that the DUP had never claimed the Government’s Safeguarding the Union command paper had resolved all the issues around checks and restrictions on goods moving from Great Britain to Northern Ireland.

He insisted he had been consistent in characterising the deal as having made some progress to address his party’s concerns over trade and sovereignty, but that more work was still required on outstanding issues.

Mr Robinson found himself unexpectedly elevated to the party leadership, initially on an interim basis, when his predecessor Sir Jeffrey Donaldson stood down in March after being charged with historical sexual offences.

Donaldson’s case is now before the courts, and he has indicated he will contest all 11 charges facing him.

The barrister-turned-politician, who is hoping to hold off a challenge from Alliance Party leader Naomi Long to retain his parliamentary seat in East Belfast, said being thrust into the leadership role in such circumstances had created a “new dynamic” in his professional and personal life.

In his interview with PA, Mr Robinson offered his view on the relative strength of the union between Great Britain and Northern Ireland – given the turbulence created by Brexit and intensifying calls from within nationalism for a border poll.

Asked to predict what the future might be for Northern Ireland in 50 years’ time, he replied: “I hope it will be at peace with itself. But I can guarantee you it’ll be part of the Union.

“We can only look back over the last 25 years that despite the enthusiastic calls for a united Ireland from some, they haven’t grown the percentage share of nationalist support in Northern Ireland one bit in the last 25 years.

“Sometimes they get a little bit of energy about what it is they have to say. But they can point to no tangible progress over the last 25 years at all. And there’s a growing and a burgeoning community within Northern Ireland who want to proudly speak of this place, speak of Northern Ireland, talk of it proudly as their home, somewhere they are proud to be from and they recognise the benefits of Northern Ireland being part of the United Kingdom.

“So, I’m very confident about our position, not only as unionists within Northern Ireland, but for the United Kingdom as a whole and the four constituent parts.

“Indeed, the biggest threat to the Union in the last number of years has not been in Northern Ireland. It’s been outside of Northern Ireland. And yet that is settled, you can see support for independence in Scotland dissipating. And, so, I think there’s a strong and positive future for the Union in 50 years and beyond.”

He added: “I don’t think there is any complacency at all, there’s always a danger if you were to take your eye off the ball, but that’s not what we present.

“I think there’s obviously a difference between political unionism and those who are pro-Union, there is a difference with that. And there’s a burgeoning centre that don’t think every day about the constitutional question but are pleased and content to be in the Union, recognise that the Union works for them and though the last number of years have been politically fractious for a whole host of reasons, that’s not our focus – our focus is about making sure that day and daily we can highlight the benefits of being in the United Kingdom and strengthen and grow these bonds.”

His downplaying of any risk to the Union stands in contrast to one of the DUP’s unionist rivals, the Traditional Unionist Voice party, which accuses both Donaldson and Mr Robinson of botching negotiations to remove post-Brexit barriers on internal UK trade. At his election manifesto launch on Friday, TUV leader Jim Allister claimed the Union had never been in a more perilous state as a consequence.

Mr Robinson railed against that sort of interpretation, and also rejected the narrative that he had performed a U-turn on endorsing the Government command paper.

“We’re not having to counter any narrative, we’re going forward in this election with a very strong pro-Union message, recognising not only the delivery we’ve achieved over the last five years, but the opportunity for Northern Ireland to be strongly represented at Westminster, and that’s resonating with people on the doors,” he said.

“They recognise that over the last number of years we’ve not only been able to identify the problems associated with Northern Ireland Protocol, but provide solutions.

“And they recognise that we have made progress continually over cycle after cycle, and that that work remains an active part of what we are engaged with, and what we will deliver in the next parliament coming forward.”

He insisted voters were crediting the DUP for making progress on changing the contentious UK/EU agreements that govern post-Brexit trade in Northern Ireland – the Northern Ireland Protocol and its successor the Windsor Framework.

“They recognise that whenever we were told we could achieve nothing on the Northern Ireland Protocol, we kept at it,” he said.

“Whenever we were told that the European Union wouldn’t come back to the negotiating table, we kept at it and achievements we secured.

“So, with the Windsor Framework (agreed in 2023), we said very clearly whilst there was progress, it wasn’t sufficient to see restoration of devolution.

“Back in January (with the Safeguarding the Union command paper), we recognised that we had more progress, and it was sufficient to see the return of devolution. And I think that has resonated well.”

Asked about the prospect of a Labour government in London, and the potential for that to result in a closer UK relationship with the EU – something that may remove the requirement for some checks on GB to NI trade – Mr Robinson said he needed more detail on what might emerge.

“It’s very important to recognise that irrespective of the government in London, we have worked positively for the benefit of Northern Ireland,” he said.

“And so whilst we’ve had good relationships with the government that has been, we have good relationships with the opposition that has been, too.

“And, if they are in government in the coming weeks, then we’ll work with them positively for Northern Ireland, always looking at detail into what it is they wish to achieve and making sure that, irrespective of where they wish to bring this country, that it does not create, it does not strengthen, but it dilutes any of those barriers that were created as a result of the debates over the European Union in the last five years.”

He added: “I’m somebody who always look at detail on this. Broad brush (comments on EU relations from Labour to date) and people are campaigning at the moment. That’s the poetry; we need to look at the prose.

“And, so, if Labour form the next government, we will engage with them productively for the people of Northern Ireland, and study in detail and work with them collectively to our benefit here in Northern Ireland.”