Tailyn Wang was two months pregnant when federal police officers broke into her house in Mexico City, ripped off her nightgown and threw her to the ground. They groped her breasts while punching and kicking her in front of her terrified children, before taking her blindfolded to a police base – without an arrest warrant.

The officers continued to physically and sexually abuse her until she miscarried in the attorney general’s office in Mexico City. Instead of receiving medical attention, she was transferred, still bleeding, to a prison hundreds of miles away. Here, several days after the illegal arrest, Wang was told she was accused of kidnap and organised crime.

More than two years later, Wang, a 35-year-old Peruvian cook, remains in prison awaiting trial, struggling with severe pain in her jaw, shoulders and back. Her mother has been granted a humanitarian visa in Mexico to care for her three traumatized children, now aged seven, 10 and 17.

Tailyn Wang, a Peruvian cook illegally arrested and assaulted in Mexico. Photograph: Courtesy of the Wang Family

Wang is one of scores of innocent women illegally arrested and tortured by Mexican security services looking to boost arrest figures to justify the war on drugs, according to damning new research by Amnesty International.

Electric shocks to the genitals, rape with objects, fingers, firearms and the penis, severe beatings and near-asphyxiation, are just some of the brutal abuses routinely inflicted on women during arrest and interrogation with almost total impunity.

Of the 100 women interviewed for the report, 72 said they were sexually abused during or soon after the arrest. Ten of the women were pregnant when arrested; eight subsequently suffered a miscarriage.

Every single woman interviewed reported psychological abuse such as rape threats against their families and sexually harassment. The vast majority were young, poor, single mothers.

Only two of the women, who gained nothing from participating in the research, said they were guilty. Most spend years in prison awaiting trial, without access to adequate healthcare or legal advice.

Wang, who has reported the torture to judges, prosecutors, doctors, and the National Commission for Human Rights, was falsely accused by an acquaintance, a local police officer, after he was also tortured.

“Instead of investigating the torture I suffered, the whole system has ignored it, including the doctors, who instead pressure me to take psychiatric drugs to shut me up,” Wang told the Guardian from prison.

Reports of torture have increased exponentially in Mexico since former President Felipe Calderón first deployed tens of thousands of armed forces on the streets to combat warring drug cartels and organised crime.

In April, leaked video footage of a female suspect being suffocated with a plastic bag by police and military officers forced an unprecedented apology from senior government officials.

But despite the introduction of numerous protocols, training programmes and specialist units to combat the problem, only a handful of perpetrators have ever been prosecuted, Amnesty found.

The navy, which has been deployed in some of the most violent states such as Veracruz and Tamaulipas, appears to have a particularly serious torture problem.

Among the women interviewed by Amnesty, eight out of the ten arrested by the navy were raped.

Magdalena Saavedra, a beautician from San Luis Potosi, said she was suffocated, given electric shocks and repeatedly brutally raped by navy officers on Mother’s Day 2013, who wrongly accused her of working with a major drug cartel.

Saavedra’s family spent weeks looking for her in hospitals and police stations until they found an online newspaper reporting she’d been charged with organised crime, drugs and weapons offences.

Her mother, who asked to remain anonymous for fear of reprisals, said: “When we finally found her, she wasn’t my daughter anymore, they’d destroyed her. They made her sign a confession by threatening to rape and kill her children. She’s locked up and we still don’t understand why, how can we talk about justice?”

Three years later Saavedra bears deep physical and psychological scars, yet the navy doctor gave her a clean bill of health, said Madeleine Penman, Amnesty’s Mexico researcher.

A unit to promote and protect human rights in the navy was announced in May. Meanwhile, a new torture law remains stuck in Congress.

“State doctors, defense lawyers and public prosecutors witness hordes of detainees brought to them by police who are completely beaten up and broken down, and they seem to treat it as a normal part of their everyday work. It is shocking to see the culture of cover up that exists,” Penman said

Wang, who is facing a long prison sentence despite no evidence against her, said: “The prisons are full of innocent women who were tortured, each of their families have been devastated, but nobody is listening.”