Concern about torture is highest in Brazil and Mexico, where 80 percent and 64 percent of people respectively said they would not feel safe from torture if arrested, and lowest in Australia and Britain, at 16 and 15 percent each, the poll showed.
"Although governments have prohibited this dehumanising practice in law and have recognised global disgust at its existence, many of them are carrying out torture or facilitating it in practice", Amnesty said in a new report.
Of the more than 21,000 people in 21 countries surveyed for Amnesty by GlobeScan, 44 percent said they would not feel safe from torture if arrested in their home country.
Four out of five wanted clear laws to prevent torture and 60 percent overall supported the idea that torture is not justified under any circumstances - though a majority of people surveyed in China and India felt it could sometimes be justified.
Amnesty said 155 countries have ratified the 30-year-old United Nation Convention Against Torture which was started 30 years ago but many governments were still "betraying their responsibility".
"Three decades from the convention and more than 65 years after the Universal Declaration of Human Rights torture is not just alive and well. It is flourishing," read Amnesty's report "Torture in 2014 - 30 Years of Broken Promises".
Amnesty said it had received reports of torture being used in more 140 countries and the report gave examples from countries ranging from Nigeria to Mexico and the Ukraine.
In August 2012, Mexican marines broke into Claudia Medina's home in Veracruz and took her to the local navy base where she was given electric shocks, forced to inhale a very spicy sauce and wrapped in plastic while beaten up, Medina said.
She denied the charge of being a member of a criminal gang but was forced to sign a confession she had not even read. "If they had not tortured me, I would not have signed the statement," Medina was quoted as saying in the report.
In January 2014, Ukrainian police detained and tortured 23-year-old computer programmer Vladislav Tsilytskiy after protests in Kiev which led to the overthrow of the pro-Russian president Viktor Yanukovich, according to another case cited by Amnesty.
His hospital report listed injuries including "skull and facial fractures, including of the eye socket; concussion and bruising, including around the neck".
"Rather than respecting the rule of law through zero-tolerance of torture, governments persistently and routinely lie about it to their own people and to the world," Amnesty said.
© Thomson Reuters 2014