Chaotic scenes at Calais that led to the Channel Tunnel being shut after migrants attempted to climb aboard UK-bound lorries are "totally unacceptable", David Cameron has said.
he British prime minister said it was important to work with the French and there was "no point either side trying to point the finger of blame".
Services through the tunnel were returning to normal today after the day of disruption caused by striking French ferry workers.
Migrants must be better documented and fingerprinted but "a lot of that needs to happen in Italy where they land", Mr Cameron told British MPs.
Work was already under way with the French authorities to improve security at Calais, including an investment of £12m (€16.8m), but the UK prime minister said he is "happy for us to do more if that is necessary".
More must be done to "break the link" between migrants getting in a boat and heading for Europe, as well as making it tougher for illegal immigrants heading to Britain, he added.
During prime minister's questions, Mr Cameron said: "It is totally unacceptable scenes that we have all been witnessing in the last day."
Migrants were risking life and limb trying to brazenly clamber aboard UK-bound trucks in Calais, with some saying they will do whatever it takes to cross the Channel.
French police had reportedly found 350 migrants hidden in cars and trucks between 6am and 10am this morning.
As trucks slowed in queueing traffic on the main road leading to the Port of Calais, migrants swarmed around them in an effort to stow away.
One migrant, a 20-year-old Syrian called Yazan, said: "My future would be better if I get to England.
"I need to get to England. I came here via Turkey and Greece and now I'm living in the jungle in Calais. The situation here is very bad.
"But life in Syria was worse. Our homes were destroyed and our government used chemical weapons against us. I need a better life in England and I will do whatever it takes."
The day of problems came amid the worsening migrant plight near the Port of Calais, where numbers at the camp dubbed the Jungle II have swelled to more than 3,000 since April.