Two attempts to board the unnamed ship were made, prompting Calais mayor Natacha Bouchart to threaten to close the port of Calais, claiming the UK was not doing enough to deter hundreds of migrants gathering in the town.

Ramps to the ferry were raised and police moved in after port security was overwhelmed, AFP said.

P&O confirmed a huge intrusion at Calais and said it had closed all doors to the vessel.