"In less than 15 days, the CRIIRAD has been informed of four malfunctions in four nuclear plants, leading to the accidental contamination of 126 workers," CRIIRAD head Corinne Castanier told Reuters in an interview.

"This is the first time I have seen so many people being contaminated in such a short period of time."

On Wednesday alone, some 100 staff at the nuclear power plant of Tricastin in southeastern France were contaminated with low doses of radiation.

The incident followed another on July 7 at the same site, which shook public confidence in the safety of France's nuclear industry, the largest in Europe, at a time when President Nicolas Sarkozy has pledged to expand it.

The French nuclear safety body, ASN, said that in 2007, less than a 100 nuclear workers had been contaminated by radiation in France, where 80 percent of power is produced by atomic energy.

The CRIIRAD also criticised French state-owned nuclear operator EDF for saying the latest contamination incident had no impact on people's health or on the environment because the radiation doses were below the regulatory limits set by international standards.

"The regulatory limits for radiation... do not mean there is no risk but relate to a maximum risk level that can be permitted," the CRIIRAD said in a note published on its website on Thursday.

The CRIIRAD was created in 1986 to give independent nuclear expertise after the French government wrongly claimed the Chernobyl radioactive cloud had stopped at the Italian border and told the population no safety measures were needed.

Castanier added that the morale of staff at nuclear power plants was especially low and the number of calls her organisation had received in the last year had soared.

The calls came from staff and temporary workers at nuclear sites, who informed them about the worsening working conditions.

Pressure was especially acute during maintenance periods at reactors, which have considerably shortened, the CRIIRAD added.

(Editing by Francois Murphy)