Under current legislation, firms are able to send temporary workers from low-wage countries to richer nations without having to pay their local social charges.
However, the French president is demanding that changes are made and is using fears about the possible collapse of the Brussels bloc to scare EU members into backing his proposals.
Speaking in Bucharest, President Macron said: “Some political or business circles seek to use the EU’s funds while at the same time developing a system of social and fiscal dumping.”
He warned a lack of support for his reforms “will lead to the dismantling of the European Union”.
He added: ”Public opinion in more developed countries with higher salaries will not accept the system in its current format.”
The current legislation – which allows firms do not have to make contributions to the host country’s health and welfare systems – has been dubbed “social dumping”, and Mr Macron believes he has a plan to reduce its effect on the host nations’ economies.
His proposal, which is backed by Germany and Austria, would limit the job duration of the detached employees to 12 months – half of the period proposed by the EU’s executive Commission.
The row is driving a wedge between the richer EU nations and their poorer neighbours, where most of the cheap labour comes from.
Poland and Hungary have staunchly refused to back Mr Macron’s plans, with Polish prime minister Beata Szydlo insisting her country would “not change its stance”.
She said: “We will defend our position to the very end, because it is a position that is in the interests of Polish workers.”
Meanwhile Macron’s plans only received lukewarm support when he visited Romania today, with president Klaus Iohannis telling him the concerns of countries in the east needed addressing, as well as those of the west.
Czech leader Bohuslav Sobotka demanded a say in discussions of the EU’s future after meeting the French president in Austria yesterday.
He tweeted: “In Salzburg, I declared the strong interest of the Czech Republic to be present at the discussion about the future of Europe and also to influence it.”
Speaking about the posted workers directive, the French president said: “The single European market and the free movement of workers is not meant to create a race to the bottom in terms of social regulations.
“I think that Europe should protect [its citizens], and in that way, the European integration project should get a new meaning. Ultimately our citizens want to free themselves from the pressures of globalisation.
“A Europe that protects is also in the position to solve the problem of posted workers. The posted workers directive, as it currently works, is a betrayal of the European spirit… This only fuels populism in our countries.”