The economists - Philippe Aghion, Philippe Martin and Jean Pisani-Ferry - complain the government has acquired an "image of an administration that is indifferent to social issues" in a confidential note to the president leaked to Le Monde newspaper.
A growing number of French people, "including some of the most fervent supporters in 2017", are disillusioned, they warn and "many of those who supported the candidate are expressing the fear of a reorientation to the right".
While welcoming such measures as the reduction of class sizes in schools in deprived areas, they say the whole package so far "does not measure up to the initial ambitions".
Tax cuts for wealthy
Echoing one complaint of ex-Socialist REM MPs, they point out that the most important ministries have gone to defectors from the mainstream-right Republicans.
Prime Minister Edouard Philippe, Economy Minister Bruno Le Maire and Budget Minister Gérard Darmanin are all former members of the party.
"We have to liberalise but we must also protect," the economists say, suggesting that some of Macron's manifesto commitments - bonus-malus short-term contracts, employee representation on company boards - should be revived and that tax breaks for business should be overhauled.
Although the government has introduced controversial cuts for top-paying taxpayers, it has yet to reduce aid to businesses.
In May Darmanin promised to cut five billion euros in business subsidies by 2022.
The statement comes as divisions begin to appear in REM ranks, notably over the planned immigration law.
Last week Phlippe appealed for more "solidarity" from the party's MPs and called on them to act collectively.