Mexican journalist, author and campaigner Lydia Cacho is in London this week to rally support for those who risk their lives to expose corruption

“I suddenly had a clearer understanding than ever of the power that journalism has to give a voice to those who have been silenced by the crushing weight of violence.”

So wrote Mexico’s best-known journalist and human rights campaigner, Lydia Cacho, upon seeing her colleagues from the press gather to cover her arrival for interrogation before judges at Puebla, central Mexico, after what she calls a “legal kidnap” by the police.

The first stage of that prolonged ordeal 10 years ago had been a terrifying 36-hour drive from her home in the coastal state of Quintana Roo to the courthouse and jail, during which she had been sexually violated, threatened with death and “disappearance”, and horribly intimidated.

Cacho was to be charged with libel after the publication of a book, The Demons of Eden, which revealed a sex-trafficking and pederast-paedophile ring with connections to power on high. The appalling story of power’s revenge, its searing impact on Cacho and the implications of the affair for all reporters is told in a further book, Memorias de una Infamia (Memories of Infamy), in which, vindicated by subsequent events and trials, Cacho demonstrates that the pederasts and sex criminals were protected by the governor of Puebla state, by the judiciary and by people even higher up – with connections also to drug trafficking.

The foreword is written by the one reporter who worked alongside Cacho during her ordeal, revealing crucial material – including phone taps – that swung the narrative from the jaws of incarceration and torture into her favour. This was Carmen Aristegui, Mexico’s most famous broadcaster, who was sacked last month by her employer, MVS Radio, after revealing that the wife of President Enrique Peña Nieto had acquired a vast luxury property from a group that had won several lucrative government contracts.

The fate of the two journalists has stirred to fever pitch the discourse about repression of free speech and the acute physical dangers faced by journalists in Mexico. Scores of reporters have been killed – often tortured and decapitated – in what is now seen as a pincer-movement against their work by drug cartels and the state.

The Los Angeles Times reported: “The loss of one of Mexico’s most critical journalistic voices comes as revelations of corruption and killings by police and the army have roiled the country and plunged Peña Nieto into the worst crisis of his 27-month presidency.”

While all this was happening last month, Peña Nieto was a guest of the Queen and the British government.

Cacho – who has won innumerable awards for her work and was made a Chevalier d’Honneur of the French Republic – will rally support this week for Aristegui and her endangered colleagues at the London Book Fair, part of a PEN festival focusing on Mexico.

Ahead of her visit, Cacho told the Observer: “After all these years, every time my mobile phone rings and I see the name of a colleague I fear the worst: assassination, kidnapping or forced disappearance. When I was arrested 10 years ago, I was not so well-known, at least not to the broader news readers; now I’ve published 10 books and still live under tremendous pressure from corrupted politicians and traffickers who want me either dead or exiled and silenced.”

Of her friend, Cacho added: “Carmen Aristegui is probably the most famous newscast journalist in our country. She was fired most probably for investigating the president, which happened months after I was fired from El Universal, one of the main national newspapers. If this is happening to us, the visible ones, can you imagine what local reporters are going through in the provinces, where rule of law is almost nonexistent?”

Facebook Twitter Pinterest Campaigning journalist Carmen Aristegui. Photograph: Gregory Bull/Associated Press

Cacho thinks the timing of Aristegui’s firing is accounted for by “the return of the PRI party, who ruled Mexico for more than 70 years. Peña Nieto’s advisers are obsessed with protecting his image at all costs. It seems they want us back into the 1980s, when nobody dared to investigate the president and his ministers.

“Aristegui’s team not only uncovered the fact that the president’s wife and his finance minister, [Luis] Videgaray, had received a couple of luxurious residences from a big construction conglomerate that was doing business with the federal government; they also exposed a network of corruption, a radiography of how the president is managing the country’s finances as if he was a feudal lord, as if laws, international treaties and transparency did not exist. This case exposes, once again, how a small group of politicians and tycoons handle all media permits in order to control freedom of expression, and they do so through monopolies and the destruction, persecution of free media and journalists.”

A report published by the London-based Article 19 organisation at the end of March and launched in Mexico City by Aristegui and Cacho – found that “under the current administration headed by Enrique Peña Nieto, the number of assaults on the press was nearly double that reported during [his predecessor] Felipe Calderón’s term of office … Failures in the justice system continue to prevail.”

According to a report by Mexico’s National Human Rights Commission in January, 97 reporters have been killed over the past four years for doing their job. There have been 22 disappearances of reporters and 433 registered attacks since 2005, when the current drug cartel war began in earnest.

Just as the report appeared, a long line of murderous attacks on reporters in the state of Veracruz culminated in the discovery of the decapitated body of a freelance website reporter, Moisés Sánchez, who had disappeared in the small town of Medellín de Bravo. The mayor of the town has been charged with having ordered the murder, but activists believe the attacks on reporters – 13 in Veracruz alone – have been orchestrated on higher authority, in the state administration. Among the victims in Veracruz was Regina Martínez, a reporter for Proceso magazine, who had been seeking to establish those connections. Her violated and tortured body was found in 2012.

In her book, Cacho differentiates between “fame”, which she sees as something “for artists”, and notoriety, which she says she has achieved simply by refusing to be silenced. Either way, her struggle has become what the great anti-mafia writer Roberto Saviano calls “the Lydia Cacho cause”.

In her London appearances, Cacho will also focus on violence against women, and lifting the impunity of those who violate them. Ahead of the visit she said: “When Peña Nieto was governor of the state of Mexico [in the south of the country] the femicide rate went through the roof: up by 185%, according to specialist Humberto Padgett. Young women were being assassinated relentlessly. Some were taken by the cartels for sex trafficking; others, younger than 15, exploited as slaves in the opium and marijuana fields..

“Peña Nieto denied everything; on his way to the presidency he could have been the hero, approving gender equality laws, forcing the justice system to act as law requires. Instead he ordered journalists to be quiet, his team bought some off, and the honest ones had to flee the region, or where threatened, or killed by unknown criminals”.

A woman of passion as well as courage, Cacho surveys the scene: “These are dark times for our country,” she says by telephone from Quintana Roo. “Civil society is confronting the powers that be, but the free media is becoming smaller day by day; narco lords rule some states and provinces. There are not enough hours in a day to help those voices that need listening to, those hundreds of thousands of victimised families that need seeing. Journalism is essential in a country that lives in a silenced war, a masked war. They can erase us journalists from the mainstream media, and they can eliminate us physically. What they will never be able to do is deny the true stories, snatch away my voice, our voices and our words. As long as we are alive we will continue to write and what we have written will keep us alive”.

Cacho recalls the last time she talked to her colleague and friend Anna Politkovskaya. “We laughed in a hotel room, we talked about family and children, about love and work, we discussed the risk of our jobs. One morning watching the news I froze as I heard she had been assassinated after coming back from buying food for her family. This fact made me aware of my own mortality.”

But by way of a message to herald her arrival in Britain, Cacho insists: “I am a woman who will not give up her rights, nor will I sacrifice the rights of others to have a comfortable living. Being a journalist in Mexico is not a job; it’s a calling, a responsibility, never a sacrifice. It is to be part of the counter-power that makes life worth living.”

Lydia Cacho will appear at a British Council event at the London Book Fair, Gallery Theatre, Kensington Olympia, on Tuesday; and for English PEN at the Free Word Centre, Farringdon Road, London, on Thursday. Slavery Inc: the Untold Story of International Sex Trafficking, is published by Portobello Books