LONDON (Reuters) - With a quip about British fog and French frogs, Paris began an advertising campaign on Monday aimed at poaching business from London after the Brexit vote raised questions about the future dominance of Europe’s top financial capital.

General view of the skyline of La Defense business district from Paris, France, October 12, 2016. REUTERS/Charles Platiau

Billboards showing a green frog wearing a tie sporting the colours of the French flag and the slogan “Tired of the fog? Try the Frogs! Choose Paris La Defense” are being put up at London’s Heathrow Airport and the London train station of the Eurostar, showcasing the French capital’s business district.

The June 23 vote to leave the EU took many investors and chief executives by surprise, triggering the deepest political and financial turmoil in Britain since World War Two and the biggest one-day fall in sterling against the dollar.

Some bankers have warned that London could gradually lose its position as the only financial capital to rival New York because foreign banks could move out after Brexit, draining London of talent, wealth and trading revenues.

London accounts for 41 percent of global foreign exchange turnover, more than double the nearest competitor, New York, according to the Bank for International Settlements. London’s closest European competitors are Switzerland and Paris, which each take about 3 percent of global foreign exchange turnover.

Around 85 percent of European-based hedge funds are based in London, which is also the leading market for international insurance and reinsurance.

Officials from La Defense business district said the adverts were aimed at underscoring the attractiveness of the French capital’s financial powerhouse, which it said had lower rentals and good public transport.

“As regrettable as Britain’s exit from the European Union may be, we have to be pragmatic and promote our own assets,” Patrick Devedjian, head of the elected council representing the Hauts-de-Seine district where La Defense is located, said in a statement.

Marie-Cecile Guillaume, director general of Defacto, a public body involved in managing La Defense, said the campaign aimed to roll out “the blue, white and red carpet for thousands of professionals now seeking new European headquarters.”

This summer the French government introduced extra tax concessions for expatriates in the hope Paris could profit from Brexit, but experts say other centres with more flexible labour and tax rules are likely to be bigger beneficiaries.

French President Francois Hollande said on Saturday that Britain’s decision to leave the European Union should not jeopardize the bloc’s principle of free movement.

“They have decided to leave. I think the worst attitude would be to contest their choice or call into question the very foundations of the European Union,” Hollande told a conference on Europe in Paris.