The Freight Transport Association (FTA) said forming a customs union with the European Union would not remove the need for checks at the borders or deliver frictionless arrangements on its own.
The warning comes as the MPs at the UK House of Commons prepares to vote on a motion on customs and borders today (26 April).
The FTA added consequences of leaving the single market should also be considered and solutions found to minimise regulatory barriers, remove the need for conformity or food safety checks at the borders, and to protect transport connectivity after Brexit.
FTA’s Deputy Chief Executive, James Hookham said: “Leaving the EU Customs Union and single market has big consequences for supply chains and the continuity of the UK’s European trade. If the Government remains fixed on this course, then it must prioritise sorting out the potential ‘showstoppers’ that will kick in on Day One of Brexit.”
He added: “Leaving the Customs Union is only one part of the story, and a customs union on its own would not remove the need for checks at the borders or provide frictionless trade for businesses. Ending of all the single market arrangements could cause even bigger delays, disruptions to integrated supply chains and barriers to trade.
“Leaving the single market would mean new checks on food safety or product conformity needing to be made at the EU border, unless less intrusive arrangements can be negotiated and implemented in time.”