“They are crystal clear about their underlying objective: the weakening of Britain, the ongoing degradation of the City of London,” Jeremy Browne, a former government minister who is now the City's Brexit envoy, said in a memo.
The leaked report, published by the Mail on Sunday tabloid, was written as a summary to ministers of a trip made by Browne to France in early July.
“The meeting with the French Central Bank was the worst I have had anywhere in the EU. They are in favour of the hardest Brexit. They want disruption,” he said.
Browne acknowledged there may be political benefits to France of playing “bad cop” in the negotiations on Britain's withdrawal from the European Union, which began last month and are due to resume in Brussels on Monday.
But “we should nevertheless have our eyes open that France sees Britain and the City of London as adversaries, not partners”.
This approach was not confined to a few officials, but was a “whole-of-France collective endeavour, made both more giddy and more assertive by the election of (Emmanuel) Macron” as president in May, according to Browne.
The Mail on Sunday headlined the story “Macron's Brexit Saboteurs”.
Browne adds that “every country, not unreasonably, is alive to the opportunities that Brexit provides, but the French go further”.
He says they are “seemingly happy to see outcomes detrimental to the City of London even if Paris is not the beneficiary”.
Paris is competing with Dublin, Frankfurt and other centres for an expected shift in finance jobs out of London as a result of Brexit.
With Britain at risk of losing the “passporting rights” financial firms use to deal with clients in the rest of the bloc, employees in direct contact with customers may need to be based on EU territory in future.
French Prime Minister Edouard Philippe earlier this month laid out a raft of measures aimed at boosting Paris's attractiveness, including eliminating the top income tax bracket.
Browne, who was an MP for the pro-European Liberal Democrats until 2015, served as a junior foreign office minister in former prime minister David Cameron's coalition government. He was appointed special representative to the EU by the City of London Corporation, which represents the financial sector, in September 2015.