Those who fear for the future of the European Union are confronting a painful paradox: Many of the strongest bids to tear apart the EU are being underwritten by EU cash.

France is careening towards a nail-biter presidential election this month that pits a crowded field against anti-EU titan Marine Le Pen. But EU funds pay her salary, fund her assistants and underwrite the conferences and books she churns out to attack the 28-nation bloc. Key British leaders of the successful Brexit campaign got their financial lifeline from Brussels euros. Elsewhere in Europe, self-identified fascists are paying for rallies to further the future of the "white race" by breaking up the EU – all thanks to EU money.

With the European Union under threat as never before, lawmakers have been pushing to tighten generous rules that make it easy for fringe political parties to qualify for hundreds of thousands of euros every year. Bigger forces – such as the European affiliate of Ms Le Pen's National Front party – get millions because of their heft in elections for the European Parliament, an institution that is short on power but flush with cash.

Some groups, such as Ms Le Pen's, are backed by a wide range of voters. But others have done little to qualify for money other than showing a scattering of support across several European countries. Some lawmakers want to end funding for those organisations.

“We have free speech, they can do lots of things, but they should not be financed by a union that is bound to totally different values,” said Marita Ulvskog, a Swedish centre-left member of the European Parliament who is fighting to stop funding for extreme-right parties.

The group she has targeted, the Alliance for Peace and Freedom, is slated to receive $723,000 (£577,000) this year. Last year, some of that money went toward a conference where a British National Party leader, Nick Griffin, said that white people “have a catastrophically low birthrate.”

Why is the rural idyll I call home voting for Marine Le Pen? Show all 3 1 /3 Why is the rural idyll I call home voting for Marine Le Pen? Why is the rural idyll I call home voting for Marine Le Pen? Pg-34-rural1-david.jpg John Lichfield in the garden of his house at Culey-le-Patry, in the Calvados region of “Norman Switzerland” DAVID SANDISON Why is the rural idyll I call home voting for Marine Le Pen? Pg-34-rural3-al.jpg In some Norman villages like Culey-le-Patry more than a third of voters backed Marine Le Pen’s National Front in the first-round ballot Alamy Why is the rural idyll I call home voting for Marine Le Pen? Pg-34-rural2-reu.jpg Marine Le Pen celebrates her success Reuters

“We already in most of our countries have so few young girls of childbearing age or younger that even if they each had 20 children, it would take us 80 years to restore our numbers,” said Griffin, a former member of the European Parliament.

Another member of the Alliance for Peace and Freedom, European Parliament member Udo Voigt, was convicted in Germany for inciting racial hatred by advocating that the national soccer team include only white players.

While the Alliance for Peace and Freedom takes just a tiny share of EU funding, bigger far-right beneficiaries of EU money also pose a far more potent threat.

As an elected member of European Parliament, Ms Le Pen can work full-time to undermine the EU because of her generous EU salary. Her EU-paid Eurosceptic assistants bolster her labour. Her pan-European party – an alliance of anti-EU lawmakers from across Europe – receives yet more EU money. And still more official funding funnels to an affiliated think tank that sponsors anti-EU conferences and policy papers.

As many as a third of the parliament's 751 members are Eurosceptic, including 23 members of Ms Le Pen's National Front party.

“When like Marine you come in with 23 seats, you get these mandates and assistance,” said Gerolf Annemans, who is a leader of Ms Le Pen's pan-European parliamentary group and a member of Belgium's Eurosceptic Flemish Interest party. “The various possibilities and means that you get are splendid to develop your political message.”

After decades at Europe's fringe, anti-EU parties blossomed during the 2014 elections that delivered a powerful if fractious contingent to the European Parliament, which has limited power but ample funding. Politicians benefited from a backlash to years of EU-driven austerity policies and a growing fear among voters that Europe's open borders were hurting their job prospects.

British members of the European Parliament as part of Ukip led the successful charge to pull their country out of the EU. Now Ms Le Pen is leading French members of the European Parliament to deliver the death blow if she wins France's presidency. European funding has been so critical to both groups that many politicians say the insurgents would never have threatened Europe's entrenched establishment without it.

“Without the European Parliament, you wouldn't have a Ukip or a Front National as powerful and cohesive as they are now,” said Giles Merritt, a longtime observer of the EU who leads the pro-European Friends of Europe think tank.

With only national elections to run in, “they probably would have died on the vine,” Mr Merritt said. “But the fact they were able to get substantial numbers of people in parliament, and through that, funding, that has been significant in the whole populist tide.”

In both France and Britain, a quirk of election law meant that small parties largely shut out of national politics could win big in the European Parliament. Ms Le Pen's National Front is the largest party in the French delegation to the European Parliament, but holds only two of 577 seats in France's National Assembly. Similarly, the Ukip is the largest British party in Brussels but has no seats in the House of Commons.

Eurosceptic leaders have long turned to the European Parliament as a ready source of funds and legitimacy. Ms Le Pen's father Jean-Marie, the founder of the National Front, has been elected to the body since 1984. Ukip leader Nigel Farage has held office since 1999. But only after the 2014 elections did the money truly start to expand, since it is tied to the number of lawmakers holding office.

The resources available to EU lawmakers are wide-ranging, starting with their $108,000 annual salaries plus daily stipends when parliament is in session. Each can hire up to three Brussels-based assistants, and more in their home nation. EU funds also pay for offices back home.

Le Pen's legacy: bitter battle for future of the French far right Show all 3 1 /3 Le Pen's legacy: bitter battle for future of the French far right Le Pen's legacy: bitter battle for future of the French far right Marine Le Pen has attracted the ire of the far right with her pro-abortion views and desire to modernise Le Pen's legacy: bitter battle for future of the French far right The party's current leader, Jean-Marie Le Pen REUTERS Le Pen's legacy: bitter battle for future of the French far right Bruno Gollnisch, who is popular with traditionalist hardliners, campaigning in Metz

Additional resources go toward pan-European political parties and affiliated policy think tanks. Ms Le Pen's Movement for a Europe of Nations and Freedom is slated to receive $1.8 million this year. Its think tank, which funds publications such as Enough with the euro! and sponsors anti-EU conferences, will receive another $1.1 million.

Although the European Parliament's assistants and foundations are technically forbidden from political campaigning, the lines are blurry. Both mainstream and anti-EU leaders have been cited for mixing national politics with their legislative work.

“The European Parliament is really important, because most of them at a national level, they don't get much. Because if you're not elected at national government it's difficult to get resources,” said Nathalie Brack, a professor of political science at the Free University of Brussels who has studied Eurosceptic lawmakers in the European Parliament. “It's an easy way to get the legitimacy they need. So they start with the European level and then they try to compete at the national level.”

Eurosceptic lawmakers readily acknowledge the utility of being a member of the European Parliament, which is often abbreviated to MEP.

“It creates a platform,” said Roger Helmer, a senior leader of Ukip in the European Parliament. “I could write a letter to the newspaper as a private citizen, and maybe it would get printed. But as an MEP I have a press officer and an office and a Twitter account, so I can do some campaigning.”