It is day eight in a depot in Lymm just outside Warrington, Cheshire and a lorry carrying frozen carrots and mixed herbs is still waiting for clearance to board a ferry from Birkenhead to Belfast.

Six separate customers, supermarkets and corner stores have other consignments on truck, all stuck in Lymm because the paperwork for a single pallet of carrots is missing key information.

Hundreds of miles away in Lisburn in Northern Ireland, the haulage firm’s operations team have had no luck in persuading the British supplier that the carrots that were ordered on 27 December are now, in the third week in January, classed as an export and must be accompanied by a litany of documents and certificates before the trailer can be cleared to board the ferry at Birkenhead.

Another supplier on the lorry had been struggling with the documentation requiring it to supply what is known as an “inco term”, which determines who pays the duty in any tariff but also establishes a specific record as to who is the importer. But that was resolved on day seven.

Then there was also the supplier who had provided a commodity code that was two digits short. A simple key stroke mistake could be difference between the lorry getting the red or the green light for entry to NI.

“It took half a day yesterday for me to clear the supply chain. I’ve got one more issue to go,” says the visibly stressed operations man simultaneously dealing with a sheaf of about 30 documents for another order of mixed fish stuck in England.

“It’s absolutely criminal what has been allowed to happen between these two islands that have traded with each other for so long,” says Peter Summerton, managing director of McCulla Refrigerated Transport, one of Northern Ireland’s biggest frozen and chilled food specialist haulage firms.

Half a day at his yard and offices is to lift the lid on the complexities Brexit and checks down the Irish Sea have brought to many businesses in Northern Ireland.

Under the Northern Ireland protocol, which was designed to obviate the need for infrastructure on the Irish border, all goods passing from GB to NI are subject to the EU customs code with sanitary and phyto sanitary (SPS) checks applied to 100% of food entering the region.

But Summerton says: “The only thing the Northern Ireland protocol (NIP) protects is the single market.”

Such is the dizzying array of new data that suppliers need to provide for transport across the Irish Sea that McCulla has devised its own “triage” crib sheet with a team of six new staff taking customers through a check list of 39 data fields to ensure flow of goods across the Irish Sea. Another 14 staff have been taken on to help with customs.

“Remember we are a haulage company,” says Summerton repeatedly as he talks of the regular spanners he has to remove from the haulage works.

Out in the yard the issues he faces are plain to see. As drivers fill trailers with a vast array of pallets carrying everything from meatballs to vegan ready meals and halloumi cheese for supermarkets shelves, a Dutch driver rolls in with a delivery of frozen chicken.

Martel Ten Dam left the Hook of Holland the day before, drove across England to Holyhead and cleared Dublin port “in five minutes” dropping off in Dundalk, Newry and Belfast before reaching McCulla’s in Lisburn.

“He’s allowed in just like that because he has come from the EU to the EU, but we can’t get goods in from GB,” says Summerton.

Overnight the company has been forced to turn itself into to “a data cleaning centre” as it cajoles and sometimes rows with customers to convince them of the new data they have to provide for goods going to NI.

With a population of just 1.9 million, supplies are always going to be sent in mixed loads, or groupage, meaning entire lorry loads are at risk if one supplier gets one item wrong.

Back at the new “customs” office Summerton has set up to deal with the protocol, the operations team have decided if they can’t get the last bit of data for the carrots the only option will be return them to the supplier, freeing the lorry to continue its journey to Belfast.

For McCulla, Brexit has been a double whammy with the Holyhead-Dublin port-Northern Ireland route also now snarled by the red tape facing all GB loads.

Summerton has two lorries delayed in Dublin because of the words “drumsticks” and “eggs” appeared in the paperwork. They were given the all clear after it was clarified that the drumsticks were not chicken but Swizzels sweets and the eggs were Cadbury’s Creme Eggs.

Last Wednesday Summerton spent the day before in Dublin port to see the procedures for himself with a high street supermarket boss trying to get five lorries containing dairy and other chilled and frozen food released from the port.

It took from 11am to 8pm to sort it out. “I cannot be critical of anything in Dublin port. They went out of their way to help” he said, “but each conversation took about 45 minutes and you don’t get that on a helpline.”

In a further complication for NI hauliers, those using Dublin port for access to Britain must also supply new paperwork for exporting, reducing the flexibility on ferry options needed for time or weather reasons.

“If Ireland and the EU and the UK were serious about Northern Ireland having unfettered access to GB, then we need the same access through Dublin as through Belfast, Larne or Warrenpoint,” he says.

One solution could be an “authorised drive-through point somewhere en route to Dublin on the Northern Ireland side where British officials could seal lorries certifying they were on “domestic” journeys via Dublin, he believes.

Summerton is campaigning for the complexity of checks to be simplified and new easing measures have been promised by the Northern Ireland secretary, Brandon Lewis, in the coming days. The Cabinet Office said on Sunday night new guidance has now been issued to hauliers.

But Summerton has taken some flak locally after he got involved with a briefing for the European Research Group and the shadow cabinet two weeks ago. He defends his right to seek further easements in the application of the protocol. “We are in logistics, not politics,” he says.

He argues the government promised to avoid “disruption to lives and livelihoods in Northern Ireland” in its command paper in December yet, along with the EU, imposed import checks designed for the likes of China without even stress testing them.

“They have transposed deep water sea container regulations on a just in time supply chain,” he says. “This is how Poland relates to Russia. This is not how Scotland should relate to Northern Ireland.”