Five months after the UK cut ties with the European Union, the post-Brexit "protocol" governing Northern Irish trade is sowing discontent in the province.

"Traditionally a box of seeds would take us four days to get from England to Northern Ireland," said Robin Mercer, owner of Hillmount Garden Centre in Belfast.

"It's taking four weeks now because of the paperwork involved," he told AFP. "And it costs £140 ($200) for a box of seeds whether there's £400 (worth) in the box or £600."

Britain officially left the EU in January 2020, but under the terms of the divorce, relations remained unchanged until the start of 2021.

Since then, London and Brussels have been trading on new terms, effectively keeping Northern Ireland in the EU customs union and single market for goods.

The tailored arrangements are designed to sustain Northern Ireland's fragile peace but for Mercer -- who operates three garden centres east of Belfast -- it has undermined business.

Seeds used to take four days to reach Robin Mercer's Belfast garden centre from England. Post-Brexit it is taking four weeks
Seeds used to take four days to reach Robin Mercer's Belfast garden centre from England. Post-Brexit it is taking four weeks AFP / Paul Faith

"The protocol, it needs to be abolished," he said.

Some 3,500 people were killed in violence over British rule in Northern Ireland, including at the border with the Republic of Ireland.

A 1998 peace deal ended the unrest between pro-UK unionists and pro-Ireland republicans, and border infrastructure was removed as British troops withdrew.

But the 310-mile (500-kilometre) frontier with EU member Ireland posed a problem as Brexit approached, as it is the UK's only land border with the EU.

Mercer must now buy certificates costing hundreds of pounds in order to import seeds from England
Mercer must now buy certificates costing hundreds of pounds in order to import seeds from England AFP / Paul Faith

The border was easy enough to keep open with both sides inside the EU.

But with one in and the other now out, the prospect of checks and policing on goods in transit caused alarm in Dublin, Belfast and Brussels, and fears of fresh unrest.

The "Northern Ireland Protocol" instead shifted the necessary checks to Northern Irish seaports on goods arriving from mainland Britain -- England, Scotland and Wales.

UK Prime Minister Boris Johnson promised "emphatically" that trade between mainland Britain and Northern Ireland would remain unfettered.

But Mercer, who employs about 70 staff, said that has not happened.

The "Northern Ireland Protocol", shifting checks to Northern Irish seaports on goods arriving from mainland Britain, has sparked tensions
The "Northern Ireland Protocol", shifting checks to Northern Irish seaports on goods arriving from mainland Britain, has sparked tensions AFP / PAUL FAITH

New paperwork required to ship goods across the effective EU border is costing businesses time and money -- and compounding stress caused by the coronavirus pandemic.

"Getting stock in has been a total nightmare. We have still not had one plant in from England," said Mercer.

Ulster University has predicted that economic output in Northern Ireland in 2020 would fall by as much as 9.6 percent as a result of the global health emergency.

Purchases and imports into Northern Ireland from mainland Britain vastly outweighed those arriving from Ireland and the rest of the bloc, according to official figures from 2018.

But that may be changing, according to Mercer.

"None of the hauliers are prepared to do the paperwork and all of the hold-ups. We've actually had to start buying plants from Europe," he said.

Garden centres are not alone in suffering setbacks in Northern Ireland, which already has the lowest GDP of any UK region.

In the first weeks of this year, some Northern Irish supermarkets saw food shortages, as suppliers grappled with new import rules.

Pressured by disruption, London made unilateral moves to delay until October the introduction of full custom controls on goods arriving in the province from mainland Britain.

That prompted legal action from Brussels. But Mercer fears worse is to come, amid mounting calls from politicians for the situation to be resolved.

"This is the relaxed period as far as it goes with all the rules and regulations," he said. "At the end of the year they're going to start enforcing them more."

In February, graffiti threatening port staff manning the new checkpoints caused protocol inspections to be suspended at Belfast and Larne ports.

More worryingly, rhetoric around the protocol was at the centre of unrest in unionist communities in April, fearful the "Irish Sea border" could end their place in the UK.

"We can't have a difference in our status between Northern Ireland and the rest of the United Kingdom without our consent, and we do not consent to it," David Campbell of the Loyalist Communities Council (LCC) said Wednesday.

"No other country in the world would tolerate suppliers having to issue customs declarations to move goods from one part of its own territory to the other," he told UK lawmakers.

"Why on earth would it ever be acceptable in the United Kingdom?"