Border staff are turning back 10pc of lorries leaving Britain because drivers do not have the correct paperwork, fuelling fears of a trade crisis and shortages of goods.

Complex and confusing Brexit rules have left lorries unable to cross to the Continent after their drivers failed to produce the correct customs documents, haulage chiefs said.

It will stoke concerns over huge tailbacks and mass disruption as customers burn through their Brexit stockpiles and traffic in Dover picks up again towards normal levels.

A member of the Border and Protocol Delivery Group - a government unit set up to oversee the UK's borders after the Brexit transition - told industry insiders that one in 10 trucks are being turned back at present.

Incorrect paperwork is a key problem as drivers struggle to understand the new post-Brexit trading regime. Covid tests are also an issue, with all drivers crossing the Channel to France required to have a negative result in the previous 72 hours as part of efforts to contain a highly infectious strain of coronavirus.

Vos Logistics, a Dutch company which carries industrial cargo for the automotive industry, said its trucks had been held up for days at a time on their way out of the UK. The Cabinet Office said it did not recognise the figure but blamed the majority of border delays on Covid testing issues.

The Government is currently enforcing full export controls, but import declarations can be deferred until July.

On Thursday Gerald Mayrwöger, business development manager at Vos, said he is still working on customs paperwork for trucks that have been waiting to leave the UK since Tuesday.

He said: "We are very much suffering on the southbound [route] from the UK to the western European Union."

Trucks leaving the UK have to complete a seven-step process in order to take the ferry or the Eurotunnel.

Mr Mayrwöger said the customs paperwork sometimes takes longer than the lifetime of a 24-hour permit drivers are given to pass through Kent, meaning the company is then fined.

Drivers are also getting lost looking for border offices, Mt Mayrwöger said, then having difficulties with the language barrier when they find them.

He said the company is now planning to reduce the amount of cargo it carries out of the UK due to the disruption, and said: "It's really a big, big administration challenge. We simply cannot afford it anymore."

Richard Ballantyne, chief executive of the British Ports trade association, said delays are particularly affecting fish exports. This is hitting the value of some shipments because their quality deteriorates as a result, he said.

Mr Ballantyne said: "A lot of fish is being either turned away, or just not getting through in time."

However not all companies are struggling.

Simon Sheffield, executive chairman of art shipping company Martinspeed, said: "We have sent six trucks to Europe so far, without any issues with Covid testing or customs paperwork.

"There are complaints from companies who have either not prepared properly or don’t have the knowledge to undertake customs." Mr Sheffield said he believes the new system is "efficient and working well".

Ballantyne agreed the systems themselves are working.

He said: "Just getting used to these new arrangements is going to be a challenge and if you haven't had to use [customs controls] before, then you'll definitely take a bit of time get used to them."