Two UK residents have been jailed as part of a people smuggling ring that charged £10,000 ($13,786) a person to cross to Britain.
The men, both Iranian nationals, were among 21 people sentenced in France as part of an organised crime network.
The group smuggled people across the Channel, mostly in the backs of lorries.
Hojjat Nickhoo, 38, and Ayoob Khaleghi, 33, were arrested in the UK and extradited to France for trial, the National Crime Agency said.
Investigators believe the group made more than £4 million in less than a year and smuggled at least 250 people into the UK, charging £10,000 for an adult, and £9,000 for a child.
Nickhoo, one of the leaders in the group, received a seven-year sentence, while Khaleghi received a sentence of two and a half years.
Collectively, all of the defendants in court were sentenced to a total of 81 and a half years in prison.
“The NCA worked closely with French authorities to track these men down and ensure they went before the court in France," said agency deputy director Andrea Wilson.
“Tragically, we have seen that smuggling people in the back of vehicles and other methods can have lethal consequences.
“We continue our work to tackle the people smugglers who seek to exploit UK borders and treat migrants as a commodity to be profited from, with no regard for their safety.”
Joanne Jakymec, chief crown prosecutor and head of the CPS international justice and organised crime division, said: “The Crown Prosecution Service worked closely with the NCA to support this effective prosecution in France, by securing the extradition of the two UK-based defendants and the transfer of evidence to France."
The NCA investigates criminal networks that cause the greatest harm, and has about 50 continuing investigations into networks or people in the top tier of organised immigration crime or human trafficking.
