Officials, who run ports in France and Belgium, are worried the uncertainty surrounding the transition period will make it impossible to be prepared when it ends on December 31, 2020.
Joachim Coens, chief executive of the Port of Zeebrugge in Belgium, said: ”The transition period of two years is fine, provided we know from the beginning of that transition period what we have to do.
“If this transition period means uncertainty during the transition period, then we will never be ready, never. It is not possible.”
Benoit Rochet, deputy chief executive at the Port of Calais, has also expressed concern that port authorities have not be told exactly Brexit will mean for them.
Mr Rochet said: “The most important problem is we know that there is Brexit but we don’t exactly know what Brexit means.
“The clock is running, time is running.”
Meanwhile, John Keefe, from Getlink which runs the Channel Tunnel, added they are still waiting for clarity.
Mr Keefe said: “In order to make our contingency planning we need to have a direction to go in.
“We are in a bit of a vacuum at the moment because we don’t know what the specification is,” Mr Keefe added.
The Freight Transport Association also hit out at the slow-moving Brexit negotiations, saying frustration “is building daily”.
Deputy chief executive James Hookham said: “Logistics businesses simply cannot answer their customers’ questions about how they will move goods after Brexit.
“Manufacturers and retailers are losing faith and fear that post-Brexit Britain is at real risk of becoming nothing more than a series of roadblocks at our ports and airports.
“What is really making our members angry is that these real, legitimate concerns are simply being dismissed by some members of the Government on the basis that it will not be in the EU’s interests to impose them.
“This is a reckless attitude to take and is playing chicken with crucial parts of the British economy and the livelihoods of the seven million Britons in the industry.”
Fears over European ports not being ready for Brexit comes as Iain Duncan Smith warned the UK should be ready for delays at Dover in the event France introduced “illegal” and “hidden border checks” at the Calais border crossing.
Speaking on BBC Radio 4’s Today programme, Mr Duncan Smith said: “My general view is they should anyway plan for delays.
“We already get delays at the border in Dover when the French go on strike or something you have lorries stacked back and there’s been this debate at Dover and various other ports that they ought to anyway have had a place for lorries when there is a hiatus moment.”
He also insisted the UK must plan for a no deal Brexit as he warned France against deliberately introduce punitive customs checks.
He said: “Under the WTO it is quite illegal for a country like France to put bureaucratic arrangements in place that deliberately delay the transfer of goods.
“It’s illegal. You can’t do that. That is a hidden border check and that shouldn’t be done.
“The WTO rules do not specify that you have to check everything.
“You cannot institute arbitrary checks simply for the purpose of delaying.”