The leader of Ulster Unionists has accused the DUP of facilitating a post-Brexit “mess” that has been a “killer” for Northern Ireland.

Doug Beattie said the region had been failed by a range of “invisible, ineffective and absent” MPs as legislation was agreed at Westminster that resulted in economic barriers being created between Northern Ireland and the rest of the UK.

The UUP was without representation in the House of Commons in the last parliament but Mr Beattie told a manifesto launch event that his party was in the hunt for five seats in the forthcoming General Election.

He identified South Antrim, Fermanagh and South Tyrone, Lagan Valley, North Down and East Antrim as targets for the UUP.

“Let’s be absolutely clear, we’re in the hunt here,” he told supporters at the event in east Belfast.

“We will get back to Westminster, we will have an Ulster Unionist MP sitting on those green benches. We are leading the way and others are looking at us now and seeing the threat that we are.”

Mr Beattie criticised the MPs who had represented Northern Ireland in the Commons since 2019 and the abstentionist Sinn Fein members who did not take their seats.

“We have been failed in Westminster through representation with invisible MPs, ineffective MPs and, of course, absent MPs,” he said.

“And we’ve all seen the pictures of debates about Northern Ireland, where nobody’s there apart from a few bench sentries from the other parties, and our MPs talking to themselves.

“That’s not good enough, because we haven’t enthused people – the MPs in GB – to listen to the issues that affect Northern Ireland and affect this part of the United Kingdom.

“So, we have been failed. We will set about changing that, to make people interested in what’s happening in this part of our United Kingdom, that cohesion that has been destroyed since Brexit. To bring it back again – the four nations of our kingdom.”

Speaking at the launch of the UUP’s Making Northern Ireland Work manifesto, Mr Beattie said while his party campaigned against Brexit it accepted the outcome of the referendum.

However, he said the “real killer” for Northern Ireland was the subsequent UK-EU withdrawal arrangements that have created barriers in the Irish Sea – the Northern Ireland Protocol and its successor the Windsor Framework.

He claimed the DUP had to take responsibility for the imposition of those deals.

“They facilitated the protocol, they created the mess we find ourselves in now and they now point the finger at absolutely everybody else to say ‘it was your fault’. Well, I’m pointing my finger back to say ‘no, it was your fault’,” he said.

Mr Beattie characterised the UK Government package of measures contained in January’s Safeguarding the Union command paper as a “falsehood” and said they had not removed the Irish Sea border.

He said his party would work to end the contentious trading arrangements and he highlighted a bespoke veterinary deal between the UK and EU as an important objective.

The UUP leader also spoke on the party’s role in the devolved Stormont Executive and its stewardship of the health portfolio.

The Ulster Unionists recently voted against a Stormont budget that was agreed by the other Executive parties. Former UUP health minister Robin Swann opposed the budget plan after claiming the allocation to his department would inflict significant damage on health service delivery.

Mr Beattie accused the other main Executive parties – Sinn Fein, the DUP and Alliance – of a lack of integrity and claimed their support for the budget stood in contrast to their publicly stated commitment to prioritise the health service.

He suggested the three largest parties could ultimately try to force the UUP out of the Executive, if it did not toe the line in relation to key issues, such as the budget.

“Let’s be absolutely direct here, honesty has not been the strongest point of the largest three parties in our Executive,” he said.

Mr Beattie said the budget would result in “catastrophic” cuts in health service delivery in Northern Ireland.

“And they voted for it,” he added. “Well, we didn’t and we won’t and we will stand up against it. And if we have to stand alone, we will stand alone. And if they try and force us out of the Executive then they best get on with it, because we’re not moving.”

Mr Beattie, a decorated solider and war veteran, also raised his concerns over Government defence policy and claimed the western approaches to the UK were being left unprotected.

He called for the reinstatement of an RAF base at Aldergrove in Co Antrim and said UK and Nato naval vessels should be pre-deployed to Northern Ireland ports ahead of operations in the Atlantic.

“The whole western approaches to the United Kingdom have been left open,” he said.