The UN's Committee for Human Right's warned against the "excessively broad surveillance powers" that have been granted to French intelligence services.
The 18-strong committee is responsible for reviewing compliance with the obligations imposed by the International Covenant on civil and political rights
"The committee is concerned by the powers granted to the intelligence services on digital monitoring inside and outside France," said the committee.
The statement continued: "The committee is particularly concerned that the law on military planning and the law on intelligence, grant overly broad powers for very intrusive surveillance on the basis of hardly defined broad objectives, without prior authorisation of a judge and without adequate and independent oversight mechanism."
The law has been touted by the government as a vital update to ageing regulations dating back to pre-Internet days, and was overwhelmingly passed by lawmakers from both left and right, though with dissident voices among almost every political group.
Although it had been in the pipeline for some time, the proposed law gained added support in the wake of the jihadist attacks in Paris in January that left 17 people dead.
The new French law allows authorities to spy on the digital and mobile communications of anyone linked to a "terrorist" inquiry without prior authorisation from a judge, and forces Internet service providers and phone companies to give up data upon request.
Intelligence services will have the right to place cameras and recording devices in private dwellings and install "keylogger" devices that record every key stroke on a targeted computer in real time.
The authorities will be able to keep recordings for a month, and metadata for five years.
The experts on the UN committee called on France to take measures "to guarantee that any interference in private life must conform to principles of legality, proportionality and necessity" and that any data gathering is done for specific purposes laid out beforehand.
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Despite the criticism France's top court ratified pretty much all of the new powers laid out in the bill.
That has led to criticism from internet civil liberties groups with in France.
In a statement titled "Shame on France" the group La Quadrature du Net said: "By validating almost all surveillance measures provided in the Surveillance Law adopted on 25 June, the French Constitutional Council legalises mass surveillance and endorses a historical decline in fundamental rights."