French president Emmanuel Macron, who will defend a global tax on tech giants at this weekend's G7 meeting, on Wednesday criticised a "crazy" system that gives firms a "permanent tax haven status".
"The global tech players do not contribute financially to the funding of the common good, it is not sustainable," the president told reporters.
He said he had on Monday discussed the issue with US president Donald Trump, who has strongly opposed a law passed in France last month on taxing digital companies even if their headquarters are elsewhere.
The law will affect US-based global giants like Google, Apple, Facebook and Amazon, among others.
Macron said there had been "very strong lobbying" by the tech giants.
"We must stop having people who have a permanent tax haven status," he said.
The French law aims to plug a taxation gap that has seen some internet heavyweights paying next to nothing in European countries where they make huge profits, because their legal base is in smaller EU states.
France has said it would withdraw the tax if an international agreement is reached, and Paris hopes to include all OECD countries by the end of 2020.
Economy minister Bruno Le Maire said last month France hoped to reach an agreement with the US on a universal tax on digital activities before the G7 heads of state meeting in Biarritz this weekend.