Depardieu bought a house just over the border from France, becoming the latest wealthy Frenchman after luxury magnate Bernard Arnault to look for shelter outside his native country following a series of tax hikes by Socialist President Francois Hollande.
"Going just over the border, I find that fairly pathetic," Ayrault said. "Being a Frenchman means loving your country and helping it to get back on its feet."
The "Cyrano de Bergerac" star bought a house in the Belgian village of Nechin near the border with France where 27 percent of the population is composed of French nationals, local mayor Daniel Senesael said.
Depardieu also enquired about procedures for acquiring Belgian residency, he said.
Belgian residents do not pay wealth tax, which in France is now slapped on individuals with assets over €1.3m starting at a rate of 0.25 percent, nor do they pay capital gains tax on share sales. France has also imposed a 75-percent tax on incomes exceeding €1m.
The tax hikes have been welcomed by left-wingers who say the rich must do more to help redress public finances but attacked by some wealthy personalities and foreign critics, who say it will increase tax flight and dampen investment.
Depardieu's move comes three months after Arnault, chief executive of luxury giant LVMH, caused an uproar by seeking to establish residency in Belgium - a move he said was not motivated by tax reasons.
The left-leaning Liberation daily reacted with a front-page headline next a photograph of Arnault telling him to "Get lost, you rich jerk", prompting luxury advertisers including LVMH to withdraw their advertisements.
Ayrault said he did not support the idea floated by some Socialist lawmakers to withdraw French nationality from people who sought residency abroad to lighten their tax bill.
"I'd rather appeal to people's intelligence, to their hearts," he said.