Welsh ports have seen a 30% fall in traffic as a result of Brexit, a shipping operator has said.
Ian Davies, boss of Stena Line's UK ports, said he believes the decline in traffic seen in Holyhead and Fishguard is because of the new trading relationship with the European Union and not because of the Covid-19 pandemic.
Mr Davies said the new deal has hit the logistics industry "quite hard".
"In January, we saw a big drop-off ranging from 50-60% of our freight volumes, as people really kind of got used to the new regimes and the new documentation that was required," he told the BBC Politics Wales programme on Sunday (January 23).
"I would say it caught quite a few, not so much in the haulage industry, but their customers unaware.
"But then things gradually improved but we seem to have plateaued. Currently, we're probably in the region of 30% down on our pre-pandemic 2019 volume."
He added: "Within this 30% we've seen some slight peaks and troughs which we put down to the Covid pandemic. But I think now we're probably in a position to say yes, this is really the effect post-Brexit of where we are and slight changes in the way that people are moving freight.
"If we look at the Irish Sea in its entirety, the freight volumes are roughly the same.
"What has been adversely affected is really the Welsh ports and the Welsh routes so far."
Mr Davies said his company had a long-term commitment to the ports and expected the situation to improve.
The three Welsh ports - Holyhead, Fishguard and Pembroke, supply more than 5,000 jobs to the surrounding areas.
The UK completed its formal separation from the European Union on January 1 2021.
From that date, new customs regulations have come into effect requiring greater checks on goods coming into the UK.
Not all the checks have been introduced yet with many more scheduled to start over summer 2022, which could mean more disruption.
A UK Government spokesperson said: "We have made extensive preparations and continue to work closely with port authorities, devolved administrations and other partners to deliver the systems and infrastructure needed on time."
Welsh Liberal Democrat leader Jane Dodds said: "Yet again we are seeing more evidence that the Conservatives are the party of doing half a job. There are now numerous serious problems with the Brexit deal Boris Johnson negotiated, most of which they were warned about before they signed the deal.
"Whether it's the unacceptable levels of new red tape for our hauliers and small businesses, the lack of an adequate veterinary agreement for our farmers or the impact of lost development funds on our most deprived regions, the Conservatives are failing to even attempt to address the problems they have caused on multiple fronts."