The following correction was printed in the Observer's For the Record column, Sunday 4 October 2009

In the article below we said divorce in Italy was legalised in 1974 after a referendum but divorce was legalised in 1970 and a referendum, held in 1974, failed to overturn it.

Towards the end of her career as one of Italy's most famous and loved leading ladies, the Roman actress Anna Magnani instructed her make-up artist not to conceal the lines and wrinkles on her face. "Leave them all there," she said. "I spent a lifetime earning them."

Magnani is now celebrated as a role model for a new generation of Italian feminists, galvanised by sex scandals involving prime minister Silvio Berlusconi, and a daily diet of sexist imagery in the media. Archive footage of Magnani's bon mot appears in a short documentary which has become a word-of-mouth sensation online in Italy. Il Corpo delle Donne, or The Body of Women, is an acid critique of the routine sexism that pervades commercial Italian television.

In the film Magnani's humorous dignity is contrasted with clip after clip featuring semi-naked showgirls and Botoxed presenters, all enduring programme formats designed to reveal as much flesh as is permissible at prime time, with a coruscating commentary by director Lorella Zanardo. More than half a million viewers have so far watched Il Corpo delle Donne and last month the film was shown and discussed on one of the country's most popular talk shows.

After a summer of sleaze in which Berlusconi has been variously accused of "frequenting minors", sleeping with an escort girl and holding debauched parties at his Sardinian villa, a feminist backlash is gaining momentum. The target is not only Berlusconi but the wider culture of a country in which a prime minister could survive such allegations.

According to Chiara Volpato, an academic at Milan's Bicocca University, matters hit rock bottom when Berlusconi's lawyer said his client would never pay for sex with an escort because the prime minister is merely an "end user" of women: "The choice of language really summed up how far we have sunk."

This summer a group of academics, including Volpato, persuaded 15,000 people to sign a petition asking the wives of world leaders to boycott the G8 conference in Italy in protest at the plight of women in Berlusconi's Italy.

Female judges, senators, nuns, historians and businesswomen circulated two more petitions calling for an end to sexism on television, while the European court of human rights will decide if Berlusconi can be sanctioned for sexism after two politicians, Donata Gottardi and Anna Paola Concia, complained to the court about his "continuous and repeated disrespectful statements about the lives and the dignity of women".

Last week, when journalist Maria Laura Rodotà published an open letter to Italian women in Corriere della Sera calling for a "New Feminism", she was overwhelmed with responses. "It was like uncorking a bottle," she said. Protest is also emerging on the right. An article damning Berlusconi for promoting beautiful young women to political positions has been written by academic Sofia Ventura and published by a think-tank run by Berlusconi's ally Gianfranco Fini.

Times were not always so bad. Italian women can draw inspiration from a proud record of winning rights in the 1970s, when 20,000 feminists would fill Rome's streets on protest marches. Despite fierce resistance from the Vatican, divorce was legalised in 1974 after a referendum, and parliament legalised abortion in 1978.

"In an Italy with no divorce, secret abortions and huge inequality in the home, feminism achieved nothing short of an earthquake," said Miriam Mafai, a former parliamentarian and veteran journalist who helped to launch the Italian daily La Repubblica in 1976.

But in recent years the Vatican has been making up lost ground. Abortion may be legal, but women have reported Catholic doctors refusing to supply even morning-after pills. And in the prime minister the unreconstructed Italian male has found a 21st-century hero.

Zanardo said that television was playing a crucial role in demeaning women and damaging their self-esteem: "Eighty per cent of Italians who watch TV use it as their sole source of information and 80% of the women featured on TV are either sex objects or mere decoration." As young girls bred on Italian TV increasingly dream of life as a velina, or showgirl, their mothers are often too tired to protest, she added. "Between jobs and housework, Italian women now work two hours a day longer than the European average."

For now, the modern feminist revolt remains largely confined to universities and national newspapers. Despite the flurry of activity, Ventura said she was pessimistic about rank-and-file women joining the petition-signing intellectuals who are mobilising: "The alarm is sounding in universities but not elsewhere, this is not yet a political problem. Feminism achieved a lot first time round, but evidently it did not reach deep enough."

Zanardo disagrees, claiming protest is growing outside university corridors, but people do not know where to look. "It's happening on the internet. The proof was when the University of Bologna withdrew erotic images it used in advertising after a huge online protest."

There are other signs. A risqué TV comedy show on a Berlusconi channel was moved to a later time slot after protests from a parents' group. And when a blonde model on Berlusconi's flagship football programme exposed a breast during a dance routine she was promptly sacked. "I don't think that would have happened in the past," said Zanardo.

Zanardo's website is registering complaints about lewd images on TV and is planning courses in schools "to help children defend themselves from this television". The response to Il Corpo delle Donne, she says, has been overwhelming: "People who watch Italian TV all the time have told me 'Thanks, it's the first time I really see what is going on'."