Dozens of migrants in Calais tried to storm a ferry bound for Britain amid mounting calls by France for David Cameron to help tackle illegal immigration across the Channel.
Riot police were deployed after up to 100 people breached security and tried to run up the ramp of the cross-Channel ferry.
Migrants were foiled from getting on board the MyFerryLink-operated Berlioz vessel when the crew raised the ramp and turned a fire hose on them yesterday, officials and a witness said.
A MyFerryLink spokesman said: "MyFerryLink can confirm that an incident took place in Calais yesterday, whereby several migrants entered the port and attempted to board the MyFerryLink Berlioz.
"The crew took immediate action to ensure the ship's security and the attempt was unsuccessful."
A spokesman for ferry operator P&O, whose vessel Spirit Of Britain was not stormed, said: "We approached the port and witnessed all the migrants.
"Our crew remained just in the inner harbour and didn't tie up until we were able to do so."
One passenger, John Bailey, told the BBC that he saw a large crowd of migrants on the main access road being guarded by French police, some armed with sub-machine guns.
A Border Force spokesman in the UK said the ramps on the vessel were immediately raised when a number of migrants entered the port, and none were able to board.
She said: "The incident was quickly brought under control and the French police apprehended all those involved. All freight vehicles inside the port at the time have been rescreened by Border Force."
The development came amid increasing anger across the Channel at the rising number of migrants flocking to Calais.
The port town has long been used as a staging post for desperate migrants to try to reach the shores of Britain.
But recent months have seen a big increase in their numbers and clashes have erupted between rival African migrants.
The disorder and large influx, mainly from African countries including Sudan and Eritrea, have led the mayor and deputy mayor of Calais to make direct appeals for UK help.
Calais mayor, Natacha Bouchart, this week stoked tensions by threatening to blockade the ferry port in an effort to force Britain to take action.
She said: "Have we got to block the port for (the) English to react? What have we got to do for (the) English to listen to us.
"I invite the English authorities to come to Calais to see what we suffer every day."
She has called for a "strong message" from Britain to deal with the issues faced in Calais.
And she added: "My priority is and will remain to the Calais population. The (people of) Calais can no longer be held hostage to this situation."
The French interior minister Bernard Cazeneuve has also reportedly waded into the dispute as he called for British intervention to ease the pressure.
He is said to have called on Britain to "assume their responsibilities" as he demanded more co-operation to help dismantle people-trafficking networks and called for a round-the-clock British presence in Calais.
The Home Secretary met Mr Cazeneuve last week to discuss bolstering security, Border Force officials in Britain said.
The Border Force spokesman said: "Security at the UK border is our priority, and we continue to strengthen it to stop those who have no right to enter the UK.
"We have already made improvements to security at Calais, working with the French authorities.
"We have, for instance, upgraded vehicle scanning equipment with the latest technology to detect people hiding in lorries and tankers and have increased the number of body detection dogs stationed at Calais.
"We will continue to bolster security, and the Home Secretary met the French Interior Minister Bernard Cazeneuve last week to discuss this important work."
In 2002, the French government closed the Sangatte Red Cross centre, near Calais after repeated lobbying by then home secretary David Blunkett.
And last month it was reported that Ms Bouchart was planning a state-funded camp away from local residents amid the "unbearable strain" of the high numbers of migrants.