Macron, a former merchant banker who is not a member of the Socialist Party although he sits in a Socialist government, has often angered his colleagues with statements that please employers more than they do trade unions and the left.
At Davos on Friday he declared that an employment law being drawn up by Labour Minister Myriam El Khomri would allow bosses to negotiate overtime rates at company level to rates lower than the current legal minimum.
At present overtime rates must be 25 per cent, unless unions agree to reduce them to 10 per cent.
Asked if that meant the end of the 35-hour week, one of the Socialists' most significant and controversial reforms while in power, Macron replied "De facto", although he added that workplace agreements would have to win the backing of an absolute majority of representatives elected to works councils.
The French bosses' union, Medef, has long demanded that the 35-hour week be scrapped, arguing that it undermines French competitivity.
National trade union representatives accused the minister of pushing economic liberalism and wanting the French worker to work more without earning more.
And Socialist MP Yann Galut declared that "by taking up positions that don't come from our side we are shooting ourselves in the foot".
Sources close to President François Hollande told Le Monde newspaper that workplace negotiations will be able to fix overtime rates but insisted that "the 36th hour will continue to be paid more than the 35th".
Macron was also pessimistic about prospects for French and European growth this year because of the "extremely volatile" economic and geopolitical situation internationally.
China's official statistics are rigged, he insisted, and its growth in 2015 was lower than the 6.9 per cent announced, while the price of oil, problems for emerging economies, the migrant crisis terrorism and conflict in the Middle East are all bad signs.
"So, if we're going to concentrate on anything this year, it should be reforming our economy as radically as possible," he concluded.