In a 91-page report, the New York-based body named a host of countries it said were transferring suspects to abusive states on the basis of flimsy "diplomatic assurances" that they would not be ill-treated.
"Governments that engage in torture always try to hide what they are doing, so their assurances on torture can never be trusted," said Human Rights Watch executive director Kenneth Roth.
"This is a very negative trend in international diplomacy, and its doing real damage to the global taboo against torture," he said.
The report details a dozen cases involving actual or attempted transfers of suspects to countries where torture is commonplace.
"This is a very negative trend in international diplomacy, and its doing real damage to the global taboo against torture"
Human Rights Watch
The list of abusive regimes included Algeria, Egypt, Russia, Syria, Turkey and Uzbekistan.
Among those countries that have sought assurances to effect extraditions to such nations were Austria, Britain, Canada, Germany, the Netherlands, Sweden and the United States.
Roth said the cases highlighted in the Human Rights Watch report provided mounting evidence that people who were transferred to abusive states are in fact tortured, regardless of diplomatic assurances.
"Governments that are using diplomatic assurances know full well that they don’t protect against torture," Roth said.