One of the most influential business groups in the U.K. is convinced that Brexit is causing “structural” damage to many U.K. companies by reducing trade and increasing costs.

Adam Marshall, the outgoing director-general of the British Chambers of Commerce, was blunt: “I push back pretty hard against anyone who says that all of the issues are simply around adjustment.”

For some companies, the extra layers of red tape “may in fact influence whether that business keeps going or not,” he said.

Britain’s relationship with a critical trading partner has been rocky, marked by a 40% decline in exports to the bloc in January and tensions over vaccine supplies. Prime Minister Boris Johnson’s government largely blamed the coronavirus pandemic and stockpiling effects for the drop.

But Marshall doesn’t accept that.

He said Brexit was responsible for a “large chunk” of that decline. A BCC survey of 465 firms, published in February, showed that about half of U.K. exporters were experiencing difficulties trading with the EU, mainly in the form of extra documentation, higher costs and delays to shipments.

For its part, the U.K. government has played down any Brexit impact. David Frost, Britain’s point person on relations with the EU, said on March 12 that “freight volumes between the U.K. and EU have been back to their normal levels for over a month now.”

Urging caution around the use of trade data, Marshall urged greater honesty and transparency when making claims about Brexit effects.

“If someone is telling me that freight volumes are back to normal on the basis of the number of lorries that are moving backwards and forwards, that’s not an adequate proxy,” he said. “I want to know what’s actually happening with the volume and value of the freight carried on those lorries.”