PARIS — France is not ready to let Britain get away from the European Union scot-free.

If the U.K. votes to leave on June 23, Paris will push to ensure that consequences are felt swiftly and severely to avoid emboldening anti-EU forces elsewhere in the bloc, senior EU diplomatic sources said.

France’s tough stance foreshadows major difficulties for London in the event of Brexit, as a core EU member tries to assert its influence in a reconfigured bloc and sway other countries against adopting an easygoing attitude toward Britain. Some of those countries, such as Germany, are more inclined to favor a softer approach.

The French push is focused on convincing the remaining EU countries to unwind all treaties and agreements binding the U.K. to the bloc quickly, so the divorce is sealed by withdrawing subsidies, re-evaluating trade relationships sector by sector, denying British supervisory bodies EU recognition in areas like financial services, and establishing new immigration rules, to name just a few levers, the sources said.

“If we say you are outside the EU but can keep all of the advantages, access to the single market without any solidarity, it’s a terrible message for the rest of the EU,” said a senior EU diplomat who asked not to be named due to the non-public nature of discussions. “[A painless Brexit] is impossible if we want to keep the rest of the EU present.”

The need to send a message is all the more pressing for the French political elite with the anti-EU National Front positioned to make a strong showing in the country’s 2017 presidential election. France would not be acting out of spite, officials said, and has no interest in setting off a tit-for-tat war of punitive measures.

But as a core EU member, sources said it had a responsibility to strengthen the bloc and deprive anti-EU parties — not just the FN but also the likes of Geert Wilders’ Party for Freedom in the Netherlands — of a chance to use Britain as a shining example of what life can be after the European Union.

“We should avoid a punitive logic,” said Elisabeth Guigou, Socialist head of the foreign affairs committee in France’s lower house National Assembly. “But our president was right when he said that Brexit will have serious consequences ... We will need to fight the centrifugal [political] forces, to show that we can draw conclusions from Britain’s decision.”

She added: “Britain will have to exit from all treaties with the EU. I think that process should go as quickly as possible, and it must not dominate the European Union’s whole agenda.”

Europe’s basic treaty foresees a maximum of two years of negotiations — led by the Commission, but on terms decided by the remaining 27 EU countries — before Brexit becomes a fact. Britain would retain full membership rights in the European Union until those negotiations are concluded.

But that process can be extended if all 27 other EU countries agree to it — or potentially accelerated, if they can rapidly reach common positions on the terms of a new relationship with Britain. France, though it carries a lot of weight in discussions affecting the EU treaties, won’t be the only country with strong views on how Britain should be dealt with during the divorce proceedings; Germany, the bloc’s most powerful member, has an interest in keeping a strong relationship with the U.K., and other regional blocs of countries will also have a say.

But diplomats said there will be clear push to get the Brexit process done quickly if Britain votes to leave.

Stumbling blocks

There are some areas in which France is unlikely to press for tough terms. For example, imposing restrictions on visa or travel rights for some 200,000 Brits who live in France (of which 69,000 are pensioners) could backfire. France has some 160,000 citizens living in Britain, who could be targeted in turn by visa restrictions on foreign travelers and workers.

“[The French] don’t want to create an EU economic cold war,” said Petros Fassoulas, secretary general of European Movement International, a leading pro-EU group in Brussels.

However, there are other ways of demonstrating that withdrawal from the EU can lead to painful payback. One is to restrict the “passporting” of financial services, which allows foreign-owned companies to do business with the EU via offices located in Britain. The principle works because the EU recognizes the authority of British supervisory bodies.

But in the event of Brexit, the EU may no longer recognize that authority, which could push firms to leave Britain and establish bases inside the European Union.

“I would be very tough [on this point],” said Sylvie Goulard, a French MEP who sits on the committee for economic and monetary affairs. “I see no reason to give passporting to a country that decides in a sovereign way to leave the EU... The day the U.K. leaves ... you cannot consider the British supervising authority as an authority of the EU.”

A similar logic would apply for British clearing houses, or financial institutions that act as intermediaries between buyers and sellers. Currently, Britain-based clearinghouses are supervised by the Bank of England, but comply with EU regulations. If Britain left the EU, member countries would re-evaluate whether they recognize clearing houses such as LCH.Clearnet, and may push to force all clearing houses to be based inside the EU — as the European Central Bank has already suggested should be the case.

On trade, EU countries would have to hammer out the terms of a new relationship with Britain — a process that would involve negotiations via the European Commission, and difficult debates in the Parliament and Council. Each country would seek an advantage for its own commercial interests against British competition, with France ready to lobby hard for agriculture.

Paris and other EU capitals hope that Britain would adopt Norway’s model of trade with the Union, under which it accepts all EU regulations including the free movement of workers in exchange for access to the single market.

But Michael Gove, the U.K.’s Euroskeptic secretary of state for justice, has said that Britain would no longer seek access to the single market as such. Instead, it would try to renegotiate the terms of its relationship along the lines of existing deals between the EU and outsider states like Switzerland, Bosnia, Serbia, Albania — all of which have varying levels of closeness with the bloc.

If Britain opts for restrictive terms, such as denying free movement of workers, Paris and other capitals will push for a narrower relationship, possibly including customs checks for all British products entering the bloc.

Cooling effect

As for British workers employed in the European Union, they could face much less favorable conditions if Britain rejects free movement of workers.

For example, a U.K. citizen living in France, or any other EU state, would not have automatic access to social services like public health care and public pensions, because those rights are not extended to citizens of non-EU nations.

There are also ways of affecting the quality of life for U.K. citizens living in EU countries, where many choose to retire, such as Spain or the south of France.

Unless laws on civil rights are grandfathered in to the future relationship with the U.K., British citizens would lack consumer protections, access to justice and redress when they are traveling or living abroad. Non-EU citizens would not be entitled to such rights, and would find it more difficult to sue in EU courts, sources said.

“People underestimate the rights of the EU citizen,” said the senior EU diplomat. “You may have to go through diplomatic channels to defend your rights [if the U.K. leaves the EU].”

Brexit could also complicate judicial cooperation between Britain and EU nations. After a withdrawal, British citizens would no longer enjoy the right to automatic extradition back to their home country, as they do now.

When it comes to investment, Brexit could also have a major cooling effect. Currently, France is the second biggest investor in the U.K. behind the United States with 124 projects in 2015, accounting for the creation of 8,198 jobs, according to the British government. But French investors could quickly re-evaluate future involvement in the event of Brexit.

“Our major investors are very involved in Britain” — Elisabeth Guigou

“Our major investors are very involved in Britain,” said Guigou. “I hope that Hinkley Point [a nuclear power plant project being led by France’s EDF in Britain] gets completed. But when it comes to other projects, French investors will look twice.”

Guigou also said a Britain-less EU would even try to take business away from the City of London financial district. “I can tell you there is already intense thinking about creating a financial hub on the Continent,” she said.

Regardless of how Britain votes, Paris sees an interest in consolidating the European Union and ensuring that the bloc becomes more attractive for investors, and for its own citizens.

“We will need to make sure that at the political level, at the Commission and Council, we make proposals for the future of the European Union,” said Guigou. “Europe cannot continue as it’s going at the moment. Things need to change so that citizens recognize themselves in the project once again.”