PARIS (REUTERS) - Train services between Paris and London suffered long delays on Wednesday (March 6) as French customs staff made extra security checks to highlight the pressure Britain's departure from the European Union could place on their workforce.

Train operator Eurostar said services were experiencing delays of up to two hours at the Gare du Nord in Paris because of the additional security controls.

Thousands of passengers queued up to pass through passport control as customs officials took longer questioning passengers and running bag checks.

"Feeling like a pawn in the Brexit game as I am currently stuck at Gare du Nord while French staff prove how terrible Brexit will be," passenger Lucy Hagger wrote on Twitter.

French customs workers began their protest on Monday at the northern ports of Calais and Dunkirk, where long lines of trucks built up as customs workers ran extensive checks.

The labour unions behind the protest action say the delays underline the need for more customs workers to be hired.

"We will overcome the shortcomings and lack of preparedness," the five unions said in a joint statement before launching their protests this week.

"But we want to alert the authorities to the state of disrepair of the customs administration."