Emmanuel Macron has warned Theresa May the UK will have to pay into the EU's coffers in order to secure a Brexit trade deal on financial services.
Speaking alongside the Prime Minister during his first visit to Britain since being elected, the French President insisted he was "here neither to punish nor reward" over Brexit.
But Mr Macron appeared to stick to the stance of the EU's chief Brexit negotiator Michel Barnier, who has said a post-Brexit deal on financial services is unlikely, unless the UK pays into the Brussels budget and accepts the jurisdiction of EU judges.
Outlining a choice for the UK, the French leader claimed Britain would have to opt for a relationship with the EU along the lines of that held by either Norway or Canada.
Mr Macron spoke at a joint news conference with Mrs May following a UK-France summit at Sandhurst military academy, in which the two countries struck a new border treaty and deeper defence cooperationin agreements totalling 13 separate documents.
As expected, France also offered to loan the historic Bayeux Tapestry to the UK in 2022.
Asked why the EU had suggested the UK's dominant financial services sector would not be included in a post-Brexit trade deal, Mr Macron replied: "I'm here neither to punish nor to reward.
"I want to make sure that the single market is preserved because that's very much the heart of the EU.
"So, the choice is on the British side, not on my side. There can be no differentiated access to the financial services.
"If you want access to the single market, including financial services, be my guest.
"But it means you need to contribute to the budget and acknowledge the European jurisdiction.
"Such are the rules. We know this is already a system in place for Norway."
Norway is not in the EU but enjoys full access to the single market in exchange for contributions to the bloc's budget and abiding by Brussels rules.
By contrast, Canada does not have the same obligations as part of its trade deal with the EU, but the agreement includes little in the way of access for financial services and does not give Canadian firms an EU financial services "passport".
In response to Mr Macron's comments, the Prime Minister – who has rejected the Norway/Canada choice – repeated her position that Britain would leave the EU's single market after Brexit.
But she also expressed her belief a Brexit trade deal should "cover both goods and services".
"The City of London will continue to be a major global financial centre," Mrs May said.
"That is an advantage not just for the UK, it's actually good for Europe and good for the global financial system."
The Prime Minister also spelled out her wish for a "good ongoing security relationship with the EU" after Brexit, with all the intelligence chiefs of both France and Britain having met for the first time in history earlier on Thursday.
Despite his tough talk on Brexit negotiations, Mr Macron claimed the UK and France were "making a new tapestry together" as the two national leaders announced a series of new cooperative measures.
At the forefront is a new border treaty, which will see the UK commit £44.5m to enhanced security at Calais and other Channel ports.
The processing of migrants looking to come to the UK via northern France will also be speeded up, with a reduced waiting time from six months to one month for adults and 25 days for children.
The French President branded the current situation in Calais as "not satisfactory" and claimed the new deal would allow him to meet his promise that after Brexit "migrants will no longer be in Calais".
He said: "We can either manage the border together or it will be a disastrous situation.
"It is not a gift for France. It is some joint management."
Mrs May also denied the agreement, which – unlike the French President – she notably did not describe as a treaty, was a concession to Mr Macron's demand for more UK assistance at Calais.
She insisted the agreement was in Britain's national interest and would "make the UK's borders even more secure".
In exchange for three UK Chinook helicopters being sent to Africa's Sahel region to assist French counter-terror efforts, Mr Macron has pledged French troops to a UK-led NATO battlegroup in Estonia in the face of Russian aggression.
The Prime Minister also confirmed that by 2020 up to 10,000 troops would be able to be deployed "quickly and effectively" in the face of any threat as part of the UK-France Combined Joint Expeditionary Force.
As Europe's "foremost military powers", Mrs May said it was "incumbent" on Britain and France to "demonstrate leadership" in upholding international laws.
Mrs May hailed the economic partnership between the two countries, with £71bn in UK-French trade, and outlined the creation of a new fund for student exchanges.
The Prime Minister described herself as "honoured" at the loan of the Bayeux Tapestry, which will come to the UK for the first time in more than 900 years.
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She said it would form "part of a wider cultural exchange" between the UK and France.
Mrs May and Mr Macron enjoyed a Michelin-starred lunch at a Berkshire pub earlier in the day, while the Prime Minister – speaking partly in French at a reception at London's V&A museum on Thursday night – paid tribute to the large number of French nationals living in the UK.