Vienna - France's leading anti-cult official on Thursday accused the International Helsinki Federation for Human Rights (IMFHR) of having been infiltrated by the Church of Scientology - which has been listed as a cult in a number of French government reports.
The IHFHR, based in Vienna, denounced the charge, and repeated criticism of moves in France to introduce a law against cults.
Wednesday's edition of France's Le Figaro newspaper carried an interview with the anti-cult official, Alain Vivien, in which he suggested the IHFHR had been compromised by the Church of Scientology.
The IHFHR "seems today to have passed into the hands of Scientologists and perhaps other transnational organisations", said Vivien, who heads up France's Interministerial Committee for the Struggle against Cults.
"That explains the virulent criticism of France, (which is) accused of religious discrimination," he added.
In a letter to Vivien on Thursday, IHFHR executive director Aaron Rhodes declared his "astonishment" at the charge.
He was, he wrote, "embarrassed for you and your fellow French citizens by your recourse to methods of denunciations and insinuations that remind us of those sometimes used by totalitarain and backward regimes".
In his letter, Rhodes acknowledged its Moscow office had received funding from Scientology to print a leaflet on religious freedom, but said the group had never sought to hide the source of the funding.
The Moscow office would have been better advised to have refused the funding, "to avoid abusive and insinuating responses such as your own", he added.
"We fear that the legislation that you are proposing could not easily be judged compatible with the notion of religious pluralism in a democratic society," said Rhodes.
The proposed French law would give the courts - and not just the government - the power to break up cults which have at least two convictions.
In the letter, Rhodes described the proposals as repressive and said it went against the right of freedom, association, expression and of religion.
It also endangered the rights of minorities and embodied prejudices that were not compatible with respect for rights, he added.
The IHFHR is a non-governmental organisation uniting 39 Helsinki Committees.
Its mandate is to monitor compliance with the 1975 Helsinki Final Act on human rights, which was formed by the Organisation for Security and Cooperation in Europe.
In the United States on Wednesday, members of the Church of Scientology called on the US Congress to denounce alleged religious discrimination in several European countries.
Earlier this month, the president of the Church of Scientology International, Heber Jetzsch, condemned a raid by French police on the group's Paris headquarters. - Sapa-AFP