Mr Cahn, who is also an expert in law, told French paper Le Monde: “On paper, it’s a two-way deal, but only because French police can carry out border checks in Britain.
“But the migration movement is only going in one direction.
“Migrants are trying to reach the UK from France, and not the other way around.
“The treaty moved the British border to France, which has been left to bear the brunt of the migrant crisis in Calais alone.”
The accord allows British police to carry out immigration checks in the French border town of Calais rather than in Dover, and which French officials say favours Britain.
Mr Cahn said: “France is having to deal with Britain’s immigration problems and tackle on a daily basis the flow of migrants attempting to cross the Channel.
“Britain has moved its border to France, just like the European Union has symbolically moved its borders to Libya to stem migration to Europe.
“France has quite literally become the UK’s Libya.”
France and Britain, however, are to sign a new immigration treaty at a summit between French president Emmanuel Macron and British prime minister Theresa May on Thursday.
The treaty, French officials said, will “complement” but not replace the 2003 Le Touquet deal.
France has asked Britain to provide more money and resources to tackle the migrant flows in Calais, threatening to pull out of the accord if a compromise or a new set of arrangements cannot be reached.
During her meeting with Mr Macron, Mrs May is expected to agree to take in more unaccompanied child migrants stranded in Calais, and spend some £44.5million to help boost security at the French port, where migrants regularly storm UK-bound trucks and ferries.
Mr Cahn, however, said Britain’s offer to take in more child refugees was not enough.
He said: “Why are the French only asking the British to take in more refugee children? Why aren’t they asking the Home Office to examine the case of all Calais migrants with family ties to the UK?”
Pro-Brexit lawmakers from the UK’s Conservative party have dismissed the suggestion the UK should pay more towards tackling the migrant crisis in Calais as “absurd”.