EUROFINS SCIENTIFIC, a bio-analytics firm, is the sort of enterprise that France boasts about. It is fast-growing, international and hungry to buy rivals. So people noticed when in March it decamped to Luxembourg. Observers reckon it was fleeing France's high taxes. It will soon be joined by Sword Group, a successful software firm, which voted to move to Luxembourg last month.

As France enters the final weeks of its presidential campaign, candidates are competing to promise new measures that would hurt business. François Hollande, the Socialist candidate, and the current favourite to win the second and final round on May 6th, has promised a top marginal income-tax rate of 75% for those earning over €1m ($1.3m). He has declared war on finance. If the Socialists win, he pledges, corporate taxes will rise and stock options will be outlawed.

Other countries welcome global firms. “France seems to want to keep them out,” sighs Denis Kessler, the boss of SCOR, a reinsurer. Jean-Luc Mélenchon, an even leftier candidate than Mr Hollande, has been gaining ground. Communists marched to the Bastille on March 18th to support him.

The right offers little solace. Nicolas Sarkozy, the incumbent, is unpopular partly because of his perceived closeness to fat cats. To distance himself, he has promised a new tax on French multinationals' foreign sales.

If Mr Hollande wins, he may water down his 75% income-tax rate. But it would be difficult to back away from such a bold, public pledge. And doing business in France is hard enough without such uncertainty. Companies must cope with heavy social charges, intransigent unions and political meddling. The 35-hour work week, introduced in 2000, makes it hard to get things done. Mr Hollande says he will reverse a measure Mr Sarkozy introduced to dilute its impact by exempting overtime pay from income tax and social charges.

The 75% income-tax rate is dottier than a pointilliste painting. When other levies are added, the marginal rate would top 90%. In parts of nearby Switzerland, the top rate is around 20%. French firms are already struggling to hire foreign talent.

More firms may leave. Armand Grumberg, an expert in corporate relocation at Skadden, Arps, Slate, Meagher & Flom, a law firm, says that several big companies and rich families are looking at ways to leave France. At a recent lunch for bosses of the largest listed firms, the main topic was how to get out.

Investment banks and international law firms would probably be the first to go, as they are highly mobile. Already, the two main listed banks, BNP Paribas and Société Générale, are facing queries from investors about Mr Hollande's plan to separate their retail arms from investment banking. He has also vowed to hike the corporate tax on banks from 33% to nearly 50%.

In January Paris launched a new €120m ($160m) “seed” fund to attract hedge funds. Good luck with that. Last month Britain promised to cut its top tax rate from 50% to 45%. No financial centre comes close to Mr Hollande's 75% rate (see chart). Large firms will initially find it hard to skedaddle. Those with the status of société anonyme, the most common, need a unanimous vote from shareholders. But the European Union's cross-border merger directive offers an indirect route: French firms can merge with a foreign company. Big groups also have the option of moving away the substance of their operations, meaning decision-making and research and development. Last year, Jean-Pascal Tricoire, the boss of Schneider Electric, an energy-services company, moved with his top managers to run the firm from Hong Kong (where the top tax rate is 15%). For now, the firm's headquarters and tax domicile remain in France. But for how long? Pressure to leave could come from foreign shareholders, says Serge Weinberg, the chairman of Sanofi, a drugmaker. “American, German or Middle Eastern shareholders will not tolerate not being able to get the best management because of France's tax regime,” he says. At the end of 2010, foreign shareholders held 42% of the total value of the firms in the CAC 40, the premier French stock index. That is higher than in many other countries.

It is not clear whether the 75% tax rate would apply to capital gains as well as income. As with most of the election campaign's anti-business pledges, the detail has been left vague. Mr Sarkozy has offered various definitions of what he means by “big companies”, which would have to pay his promised new tax.

Some businessfolk therefore hope that the most onerous pledges will be quietly ditched once the election is over. But many nonetheless find the campaign alarming. French politicians not only seem to hate business; they also seem to have little idea how it actually works.

The most debilitating effects of all this may be long-term. Brainy youngsters have choices. They can find jobs or set up companies more or less anywhere. The ambitious will risk their savings, borrow money and toil punishing hours to create new businesses that will, in turn, create jobs and new products. But they will not do this for 25% (or less) of the fruits of their labour. Zurich is only an hour away; French politics seem stuck in another century.