As many as 20,000 bankers and city workers may be lured out of the UK and across the Channel to set up case in the French capital, according to Europlace.
The group boasted that talent could start to leave London within weeks, after Paris pitches itself to London executives at a number of meetings in February.
Amid a struggling economy, and French elections looming the country is desperate to exploit Britain's exit from the EU for its own benefit.
French officials want to showcase Paris as a premier choice to Frankfurt, which it sees as a competitor for attracting jobs away from Britain.
Europlace aims to drum in the message that France is already to home to a number of city workers, alongside a large bond market.
But critics poured doubt on claims that London's position as a financial centre could be snatched by the cities in Europe.
A spokesperson for UKIP said: "Paris can eye up all they like: the City of London has been a financial hub since forever… English is the language of finance and the French don't even like to pretend English exists.
"But if they want to hire lobbyists over here, then great.
"More money for UK PLC. Will they be bringing croissants like Natascha Bouchart did when she went to Dover?"
It comes as Britain gears up to trigger Article 50 and begin negotiations to leave the union.