Seventeen French former ministers, women from across the political spectrum, said Sunday they would no longer remain silent about sexual harassment in politics, days after an investigation was opened into multiple claims against a former deputy parliamentary speaker.

"We will no longer keep quiet," the former ministers, all women, including current IMF chief Christine Lagarde, ex-health minister Roselyne Bachelot and ex-housing minister Cecile Duflot said in a statement published by the Journal du Dimanche weekly paper.

Also among the signatories is 89-year-old former justice secretary Monique Pelletier who recently announced that she had been sexually assaulted by a senator 37 years ago, and now feels ashamed of her own silence. They promised to "systematically denounce all sexist, remarks, inappropriate gestures, inappropriate behavior," announcing an end to the silence with which such cases have previously been met. They urged political parties and groups to verify whether such acts had taken place and, if necessary, help victims tell their stories and gain justice.

Their cross-party stand comes after French judges on Tuesday opened an investigation into multiple claims of sexual harassment against former deputy parliamentary speaker Denis Baupin, a move which experts welcomed as an end to the "omerta" around alleged abuse by politicians.

Baupin, 53, has quit his speaker's post but vigorously denies the claims and has instructed his lawyers to sue two French media outlets for defamation, calling the allegations "mendacious."

The same day Finance Minister Michel Sapin became ensnared in a sexual harassment scandal after admitting that he acted "inappropriately" towards a female journalist after twice denying any improper conduct.

Sapin acknowledged late Tuesday "making a comment" while placing his hand on the woman's back at a conference early last year. The ex-ministers in their joint comment Sunday said: "Like all women who have entered into previously exclusively male environments, we have had to either submit to or fight against sexism.

"It's not for women to adapt to these environments. It's the behavior of certain men that need to change," they added. "Enough is enough. Impunity is over."

The former ministers encouraged all victims of sexual harassment and aggression to speak up and lodge complaints. "Today the judicial arsenal exists but the laws are not sufficiently applied."

Labor laws protect employees but are not respected, with few women lodging complaints and very few of those complaints leading to convictions, they complained.

Women's Rights Minister Laurence Rossignol, speaking on the France 3 television channel later, outlined two moves to tackle the problem.

"The first is to swiftly adopt the draft law currently going through parliament... which lengthens the time limits for a range of offenses from three to six years," she said, calling upon the Senate, or upper house of parliament, to pass the measure.

The second initiative "is to allow associations to file complaints instead of the victims," through an amendment which will be examined by parliament next month, she added. Hailing the initiative of the ex-ministers, she added: "We say to men who behave this way: leave us alone. Don't forget for even 30 seconds that you should regard us women purely in the professional sense, as the bosses or the colleagues that we are. Stop judging us all the time as the targets of your quests."

One man who put his head above the parapet to enter the debate on Sunday was Prime Minister Manuel Valls who tweeted his support to the ex-ministers' initiative. But amply portraying the resistance to change in other quarters, former housing minister Duflot tweeted some of the sexist messages she had received over her support for Sunday's statement.

These included; "Duflot harassed? The guy was drunk" and "Apart from (former sports minister Chantal) Jouanno, who would want to harass these women lol?"

However Nathalie Arthaud, spokeswoman for the Workers' Union party accused the statement's signatories of having practiced "omerta" while they were in office. "They chose their career over the dignity of women," he said in televised comments.