Officers from the UK Border Agency (UKBA) raided 35 addresses in England and Scotland, 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 operation.
Stowaways can 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. Warrants were also executed in Manchester, Sheffield, Lancashire and Glasgow. More than 150 officers from the UKBA took part in the operation.