"SIGNIFICANT problems" are unfolding on the Irish Sea trade border over exports from the rest of the UK as firms struggle to meet new rules, MPs have been told.

As many as 1000 vehicles cross over each day during January.

In an evidence session, business leaders told how problems emerged on the very first ferry arriving in Belfast on January 1 as Brexit took hold - with UK firms unaware of how to comply with new rules.

Six of 15 loaded lorries on that vessel were delayed due to incomplete paperwork.

There had been no pre-notification about the contents and, on checking the manifest, officials in Belfast found it said only "food".

Delays of up to 12 hours have held back transit.

Customs declarations and, in some cases, additional certification is now required for all goods moving to Northern Ireland from elsewhere in the UK under the terms agreed between London and Brussels.

While Northern Ireland remains in the EU's single market, Scotland, England and Wales do not.

Northern Ireland Secretary Brendan Lewis has companies are managing, but Seamus Leheny of the freight trade body Logistics UK told the Northern Ireland Affairs Committee that one major Great Britain-based firm had 15 loads of food bound for NI without any customs documents - meaning hauliers had been unable to lift them.

Meanwhile, just 100 of the 285 trucks sent to Great Britain by one NI haulier since January 1 had been able to return.

Leheny said: "The knock on is that they can't service NI exports going back to GB because they've got lorries and equipment sitting in England, waiting for loads that aren't ready yet.

"This is because businesses in England, Scotland and Wales haven't been prepared."

DUP MP Ian Paisley said a "blind man on a galloping horse" could have predicted the "unmitigated disaster" and called for elements of the sea border to be unilaterally disapplied under Article 16 of the Withdrawal Agreement.

Leheny responded: "The fear is, if you invoke this, what is the alternative?

"Is it more chaos? Before you invoke Article 16 you need a realistic alternative that is going to work, you just can't simply walk away from this and think something else will be better. You need a clear plan of action on this and right now there is no clear alternative."

Aodhan Connolly, director of the Northern Ireland Retail Consortium, said: "The big message from us is that we need the EU and UK to sit down together to talk about how the systems can be simplified and how we can get a long term workable solution because, quite frankly, this is not it."

However, Lewis told BBC Radio Ulster businesses are "dealing with" the change and the flow of goods will return to 2020 levels "as things settle down".