The Brexit deal for Northern Ireland is an "unmitigated disaster" and should be suspended, the Democratic Unionist Party (DUP) has said.
At a hearing of the Commons Northern Ireland committee on Wednesday MPs heard evidence from hauliers and retailers about the problems the new arrangements were causing compared to EU membership.
MP Ian Paisley Jr, the DUP's communities spokesperson who sits on the committee, said: "They've basically told us that the protocol and its workings, on day six, is an unmitigated disaster.
"That's one of the reasons I was against it, because I think a blind man on a galloping horse could have told you it was going to be an unmitigated disaster."
Mr Paisley argued that the UK should invoke Article 16 of the agreement, which allows for its suspension in the case of "serious" economic, social, or trade disruption that is "liable to persist".
Conservative MP Simon Hoare, who chairs the committee, described the suggestion as "slightly eccentric".
It comes amid revelations that some British businesses have stopped delivering to Northern Ireland because of the extra bureaucracy Brexit has created.
No business group giving evidence at the committee on Wednesday endorsed the suggestion that the Northern Ireland protocol should be suspended, though many painted a picture of a very difficult situation.
"Before you invoke Article 16 you need a realistic alternative that's going to work. You can't just walk away from this," said Seamus Leheny, policy manager at Logistics UK, which represents freight operators.
He added: "I think to invoke Article 16 you'd create more problems compared to what we're facing today."
Mr Leheny warned that some lorries were being held at customs control for six to eight hours crossing from Great Britain to Northern Ireland for not having the right paperwork.
And he said some declarations that the government had pledged would take around 30 seconds to process were actually taking as long as 12 hours.
Other operators were completely unaware of many entry requirements, and one had had to teach itself how to fill in a customs declaration by watching a YouTube video.
And a support scheme for traders that the government had pledged would have 70 staff was left with just four people answering telephones on the opening weekend of the new arrangements.
"There's people ringing the call centre looking for assistance, it's ringing off the hook - it seems like they've been overwhelmed," he said.
Mr Leheny added: "It's the lack of preparation on the Great Britain side... everything from [small and medium enterprises] right up to blue chip companies.
"One large manufacturer in Great Britain had 15 lorryloads of food to go to Northern Ireland this week.
"Not a single one of them could move because when the lorries arrived there was no customs declaration.
"The operator quite rightly said there's no point me lifting these because I'll simply be detained or refused entry to board the ferry at Cairnryan or Liverpool."
Aodhán Connolly, director of the Northern Ireland Retail Consortium, said many companies had stopped serving Northern Ireland because of the last-minute way the new rules and been brought in.
"There were people being trained up on 30 December for restrictions that were in place on 1 January," he said.
"We've already seen that some suppliers, either because they don't understand the new regime or because it's too much hassle have opted out of serving the Northern Ireland market.
"We didn't receive the guidance from HMRC until 31 December and because of that some retailers took the decision not to service Northern Ireland. Quite a few have come back online but not all."
Mr Connolly said there was a feeling that the disruption so far amounted to "the opening skirmishes" of wider problems which would emerged more clearly in the coming weeks. He said freight traffic around New Year had been around 20 per cent of normal and that stockpiling by firms in December had helped reduce the impact.
"There are real hardships that are going to come at the middle of this month and then of course there's the deadline in April and July for the export health certificates and the restricted lists," he said.
"The big message from us is that it's great that there's been a deal and agreement on the protocol but we need the EU and UK to sit down together and talk about how the systems can be simplified and how we can get a long term workable solution because quite frankly this isn't it."
The Northern Ireland protocol was negotiated in 2019 as part of the government's Brexit withdrawal agreement, but it only came into force at the start of this year with the end of the transition period.
The protocol keeps the border between the Republic and Northern Ireland open, but at the expense of extra checks and controls on trade between Great Britain and Northern Ireland.
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