Dozens of raids have been carried out across the UK and in France and Belgium in a crackdown on people-smuggling gangs.
Officers from the UK Border Agency (UKBA) raided 35 addresses in England, targeting gangs who bring illegal immigrants into the country in the back of lorries through Channel ports.
About another 40 raids were carried out at the same time in France and Belgium as part of the same operation.
The stowaways pay from £2,000 to £6,000 per person to be smuggled into Britain.
Raids were carried out in London, Hampshire, Peterborough, Birmingham, Coventry, Smethwick, Leamington Spa, and Stoke-on-Trent, with warrants also being executed in Manchester, Sheffield and Lancashire.
More than 150 officers from the UKBA took part in the operation and it is understood many of the immigrants who pay the gangs are from Iraq, Iran and Afghanistan.
So far, officers have made 20 arrests in relation to their investigation and another six in relation to other suspected offences including immigration breaches.
Chris Foster from UKBA said: "We believe this to be one of the biggest operations of its kind ever undertaken in the UK, involving officers the length and breadth of the country. My officers have been working closely with their counterparts in France and Belgium as well as other law enforcement agencies in the UK in the build-up to the operation.
"We believe we have successfully disrupted a significant organised network suspected of being involved in a systematic attempt to evade the UK's immigration controls."