Hundreds of women who were fitted with faulty breast implants made with cheap industrial silicone not fit for humans have expressed their anger outside a courtroom on the first day of one of the biggest trials ever held in France.

Jean-Claude Mas, the founder of Poly Implant Prothèse (PIP), and four of his senior staff are on trial for aggravated fraud, accused of cutting costs for 10 years by using an illegal homemade concoction of industrial-grade and agricultural silicone in most of its implants.

The firm, which at one time was the third biggest global supplier of breast implants, became the focus of an international scandal over the botched implants, which were on the market from 2001 to 2010. It is estimated that more than 300,000 women in 65 countries may have had PIP implants fitted, including in breast reconstruction procedures after mastectomies. In France, nearly 15,000 have chosen to have their implants removed or replaced. At least 4,000 reported PIP implants rupturing.

Dressed in a blue anorak, Mas, 73, appeared in the dock as the judge read the charge sheet which said using a substandard, non-authorised gel in implants had posed dangers to women's health and a higher rate of rupture. Mas spoke only to give his address and say he was retired and lived on a €1,800 monthly pension. This prompted cries of outrage from the hundreds of female plaintiffs in court. PIP reportedly saved €1m a year from the scam.

Before the hearing several women questioned how Mas, who had worked in various jobs such as Cognac sales and insurance before setting up as the implants manufacturer in southern France, could have cynically cheated health inspectors to make cheaper, untested implant gel with apparently no concern for women's health.

"We were cheated physically, psychologically and morally, I just want him to explain to us why he did it," said Christine Michelini, 51, from Caen, who will be a witness in the trial. She was fitted with a PIP implant after cancer treatment and was operated on several times, finally having the implant removed.

Christine Micchi, 48, a sales assistant from Aix-en-Provence, paid €4,000 for PIP implants in 2007 for cosmetic reasons. She said: "Two years later, they ruptured. I had them removed, more surgery, more scars, and now I have leaked silicone in my body that has to be constantly monitored. At the start, I was on antidepressants. We hear talk of the industrial silicone used in these implants which might normally be used for electrical cables or car oils. It's a constant worry."

With over 5,100 plaintiffs and 300 lawyers, the trial is one of the biggest ever held in France and is taking place at a congress centre, because the courthouse was not big enough. Legal argument over the way the trial was being held took up most of the first day.

Outside court, Jean-Claude Guidocolli, lawyer for 10 victims, called the trial "catastrophic" because it had taken too long to come to court, "allowing the defendants to organise their insolvency" and limit potential for compensation.

He said: "From a human perspective, it is terrible: the victims are seated at the back, 100 metres behind the accused, when all they wanted was to see Mas's face. They feel frustration and anger."

He said health authorities responsible for monitoring implants should be in the dock as well, not among the plaintiffs. Alexandra Blachère, a former waitress from Besançon who had her PIP implants replaced and now runs an association for women with faulty implants, said: "The women have a need for justice and recognition. Many with problems initially weren't listened to by surgeons who said, 'It's all in your head.'"

The hearing, the first of three potential trials over PIP, will last until 17 May. Mas faces up to five years in prison and a €37,500 fine.

A separate investigation into possible involuntary homicide was opened following the 2010 cancer death of a French woman with PIP implants. In December 2011, the French health ministry advised women with PIP implants to have them removed as a precaution, cautioning that while there was no proven cancer risk, they could rupture.

Last year, medical experts investigating the consequences of the PIP scandal in the UK concluded that the substandard silicone gel did not pose a significant risk to women's health in the long term.