International banks have stepped up their enquiries and talks about switching operations from London to Paris following Britain's vote for Brexit, according to a senior official at France's markets regulator. 

"Large international banks... have already undertaken real due diligences and we have received a lot of practical questions regarding the way they are going to be managed from our perspective, with their relationship with the French regulators," Benoit de Juvigny, secretary general at the AMF.

He made his comments in an interview with BBC television last night. 

He stressed however that the enquiries remained "informal" at this stage, as did similar steps being taken by consultants and lawyers.  

Other financial centres said to be in the running include Amsterdam, Dublin, Frankfurt and Luxembourg. 

Powerful lobby group the British Bankers' Association (BBA) has warned that international lenders with operations in the UK are ready to transfer some of their activities out of the country from early 2017. 

Big banks have publicly voiced their fears about the impact of Brexit, including potential loss of access to the European single market. 

But the BBA refused to comment on the latest development. 

De Juvigny noted that while London possessed "great expertise" in the field, his own city's expertise should not be underestimated, adding that he sees the prospect of regulating banks wishing to move across the Channel as "a welcome challenge". 

"Also it is a dangerous challenge because we could see some kind of new competition between countries, between regulators," he said. 

British Prime Minister Theresa May has stated that she will formally trigger the two-year EU divorce process by the end of March 2017. 

However, Brussels and London face the daunting prospect of gruelling negotiations on future trade deals with the European Union and countries outside of the bloc. 

EU "passporting" rights currently allow financial products approved by a single regulator in a member state to be sold in the entire EU. 

But firms registered in the UK risk losing this access when Britain leaves, which could push some companies to move at least some of their activities to continental Europe.