By Chris Morris
BBC News, Delhi
Most custody deaths are a result of torture, the group says (Photo: Prashant Ravi)
Nearly 7,500 people have died in official custody in India over the past five years, according to a report by a human rights group.
The report by Delhi-based Asian Centre for Human Rights says many of these people were tortured in custody.
It says the Indian government is in a state of denial about torture.
Even when action is taken against officials who are accused of wrongdoing, the report argues, the system tries to cover up any crimes.
The Indian report was released to coincide with the United Nations' global day against torture on Thursday.
The rights group has collated official figures and found that 7,468 people - that is four people every day - have died in prison or police custody since 2002.
Nearly all the deaths, it says, were the result of torture.
But the government routinely attributes deaths in custody to illness, attempted escape, suicide and accidents.
Suhas Chakma, director of the Asian Centre for Human Rights, says prosecuting responsible officials takes a long time in India, and leads to a "culture of impunity".
"It takes about 25-30 years to prosecute somebody. And by that time many of the accused are dead, or possibly the relatives that have filed a complaint are dead," he said.
"So there is a culture of impunity which is given by the government of India, and I think this is the single most important factor which is encouraging torture."
The report also criticises an appalling record of torture among armed groups which fight against the Indian state - highlighting in particular the actions of Maoist rebels.
But the onus is on the government, it says, to improve its record.
Torture, it recommends, must be made a specific criminal offence. And the government should ratify the United Nations Convention against Torture without delay.