The expose found the migrants trying to avoid deportation to their home country by being smuggled to Italy, where they can make an asylum claim and then re-enter the UK.
A European Union (EU) asylum loophole means that, if then caught in the UK, they are likely to be returned to Italy rather than their country of origin.
An undercover BBC investigation filmed 21 illegal immigrants inside a lorry being taken on to a ferry and into France.
Some said they had entered the UK on student visas, while others came illegally and were now fleeing possible deportation.
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The 1,500 pound smuggling service was offered by an east London people smuggler.
"Most people think illegal immigrants are trying to get into the UK. All the efforts of the authorities are focused on preventing people from coming here illegally. I don't think people realise the extent of the trade of shipping people out of the UK into other parts of Europe and elsewhere in the world," John Vine, former independent chief inspector for UK Borders and Immigration, said.
The Port of Dover in the UK plans to introduce exit checks from April to curb this trend.
While being smuggled out of the UK cost just 300 pounds, the return journey is priced at 1,200 pounds as it is considered more risky.
A Home office spokesperson said the UK offered sanctuary to those who "genuinely need our protection" but took firm action to prevent illegal migration and the "abuse of our asylum system".