More than 100 migrants stormed the Calais ferry terminal in a coordinated push to board a Dover-bound ferry, forcing the authorities to delay its departure while they rounded them up yesterday.

About half of the migrants managed to scramble onto the ferry and conceal themselves on board. Two fell into the sea and were rescued.

French police arrested at least 46 migrants but were continuing to search the vessel, where it was believed several were hiding.

Some were discovered on an external catwalk attached to the ship’s funnel and firefighters were trying to persuade them to come down, according to Jean-Philippe Vennin, a Prefecture official.

“Firemen managed to get close to them but did not succeed in talking them down, so a second attempt is underway,” Mr Vennine said yesterday afternoon.

The men broke into the highly protected ferry port at just after 8.30pm on Saturday soon after the Danish-operated DFDS Seaways ferry arrived from Dover carrying 211 passengers and 75 crew members.

The migrants used a maintenance ladder to clamber aboard the ferry at high tide, according to Mr Vennin. “Two fell into the sea and were quickly rescued by firemen,” he said.

Police oversaw the offloading of all the cars and lorries arriving from Britain before carrying out a top-to-bottom search of the vessel. It was moved during the night to avoid further delays while police searched it.

At least two ferries were delayed from coming into port as police completed a search of the stormed boat credit: Philippe Huguen/AFP

Nevertheless, cross-Channel ferry traffic was delayed overnight with at least two ferries having to wait at some distance from the French coast before being allowed into port.

There are concerns that migrants desperate to reach the UK before Brexit are resorting to new tactics. While French police are accustomed to intercepting migrants trying to set off in dinghies, it is unusual for such a large group to try to storm a ferry in this way.

Gilles Debove, a Calais police union spokesman, said: “This was a coordinated, simultaneous assault and when it started there were too few police officers to intervene.

"The riot police reinforcements usually present in Calais had been sent to deal with the ‘yellow vest’ protests. As Brexit comes closer, we’re seeing more migrants try to reach England.”

The storming of the ferry came a day after a French court jailed and sentenced two Iraqis and an Iranian convicted of smuggling migrants across the Channel by boat.

A 30-year-old Iraqi received an 18-month sentence and his two accomplices, an Iranian, 30, and an Iraqi, 39, each received a year’s sentence.

Despite the closure of the “Jungle” camp at Calais, about a thousand migrants are thought to be camped out in northern France as they repeatedly try to enter Britain.

While many try to board lorries to reach the UK, there has been a jump in the numbers attempting to cross the Channel by boat. About 500 migrants tried to sail to England last year, almost all of them in November and December. In 2017, only 13 attempts were reported.

Many of those organising or undertaking the sea crossings are Iranian. HMS Mersey, a Naval patrol vessel, was deployed in the Channel to patrol for migrants in January, and Sajid Javid, the home secretary, ordered the recall of two Border Force cutters from the Mediterranean to the Channel.

Mr Javid and Christophe Castaner, the French interior minister, announced a joint action plan to deploy drones, radars and CCTV in the Channel and along the French coast.