The Gulf kingdom came under scrutiny by members of the UN Human Rights Council, which is examining Bahrain’s rights record as part of its four-yearly review process.
"France condemns the arbitrary arrests and ongoing charges against defenders of human rights, trade unionists and campaigners for simply expressing their opinions," said French ambassador to the UN in Geneva Nicolas Niemtchinow, who highlighted the case of Rajab and fellow activist Abdulhadi al-Khawaja.
Rajab, who heads the Bahrain Centre for Human Rights, has been leading anti-government protests following a brutal crackdown on Shiite-led demonstrations against the ruling Sunni Al-Khalifa dynasty in March 2011.
Rajab was detained on May 5 for "insulting a statutory body via Twitter" and also faces trial for taking part in a Manama demonstration three months ago.
Khawaja was convicted last June of plotting to overthrow the government and has been on a hunger strike since February 8.
At the meeting France requested a "humanitarian response" for the dissident and Denmark said he should be released for treatment.
The United States meanwhile called for a review of the convictions of all people involved in non-violent protest and Britain recommended new trials for all defendants convicted in military courts.
HRC members and observers welcomed the setting up of an independent commission of inquiry following the crackdown in which 35 people were killed but said more must be done to implement its recommendations.
Bahraini Human Rights Minister Salah Bin Ali Mohamed Abdulrahman said "radical measures and progressive steps" had been taken to overcome the "sad and unfortunate events" of March 2011.
Some of the recommendations required legislative amendments and this "may take some time," he said.
But the minister told the meeting Bahrain held no prisoners on charges relating to freedom of expression.
"Any such charges have been withdrawn. The only cases (remaining) are criminal cases.
"These cases are being looked at by the judiciary therefore the government cannot interfere," he said.
