After more than a month of travel chaos at the Paris terminal of Eurostar, things had seemed to be returning to normal in recent weeks.

However on Sunday evening and Monday morning passengers were again reporting long queues for passport control with delays on trains.

One Twitter user reported “500m long queues and no information on what's happening”.

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Passengers queuing at Gare du Nord during the height of the protests in March. Photo: The Local

The Gare du Nord station master described the situation on Monday morning as “very complicated and slow” with delays of up to 90 minutes.

Eurostar reported that services between Paris and London on Monday were running about an hour late.

The week marks the start of the Easter holidays for many and is expected to be a busy one.

French customs officials began a work-to-rule protest on March 4th, which led to weeks of long delays at luggage checks and Eurostar was forced to advise its passengers against all non-essential travel.

The 'no travel' advice was lifted on April 3rd and the situation had looked to be returning to normal, although French customs unions insisted that their protest was ongoing.

“We're getting back to the strike because we still haven't heard anything from the government regarding our demands,” Vincent Thomazo from the UNSA union told The Local.

“It's possible it could continue every day and also get more intense. Our agents are very angry,” he added.

Thomazo went on to say that the reason the situation had seemed to improve recently was because Eurostar passengers had been deciding not to travel or had at least been following Eurostar's instructions for queuing which had eased the situation.

The long-running protest concerns pay and conditions among the French customs staff.

Instead of going on strike, customs officers have been carrying out work-to-rule industrial action.

This means that they precisely follow all safety or other regulations, which entails lots of checks and questions which has slowed down the flow of passengers through terminals at Eurostar, Eurotunnel and the ports in Calais.

The customs agents are demanding an increase in overnight pay, a danger allowance, and more staff and resources to help with greater controls that will be put in place if and when Britain breaks away from the European Union.