The death penalty is carried out by hanging in India
Rights group Amnesty International has urged the Indian government to impose an immediate moratorium on executions and move to abolish the death penalty.
The group says there are "grave concerns about arbitrariness and discrimination" in processes leading to the death penalty.
It says 135 countries have abolished the death penalty in law or practice.
Indian authorities say the death penalty is rarely carried out and is usually reserved for serious cases.
Apart from a single execution in 2004, there have been no executions in the country in the past ten years.
A 1983 ruling by the country's Supreme Court stated that the death penalty should be imposed only in "the rarest of rare cases".
Only particularly horrific or politically sensitive cases have attracted the penalty.
In a new report, Amnesty disputes this and says the Indian government does not disclose how many people have been executed and how many are awaiting execution today.
It says, according to official figures, there were 273 people awaiting the death penalty in Indian prisons as at the end of December 2005.
The group says it "believes this figure to be a gross underestimate".
It says at least 140 people are believed to have been sentenced to death in India in 2006 and 2007.
It is not clear how the group arrived at the figure.
Indian prison authorities denounced Amnesty's claim that there was no transparency about prisoners on death row in India.
The death penalty can be imposed in cases relating to terrorism
"Death sentences are carried out under court orders. Every order is recorded and prison records sent to the federal government regularly. There is nothing hush-hush about it," said BD Sharma, the chief of prisons in eastern West Bengal state.
"Such claims are totally sensational," he said.
To put things into perspective, he said, in a big state like West Bengal, there were 12 prisoners on death row, down from 17 a few years ago.
Amnesty says it studied death penalty cases in collaboration with the Indian rights group People's Union of Civil Liberties (PUCL) for its latest report.
It says that most death sentences handed down in India are based solely on circumstantial evidence.
The report says "innocent people" have been sentenced to death on the basis of "false and fabricated evidence, often used in manipulated investigations and prosecutions, with investigating and prosecuting agencies acting in collusion".
Amnesty urged the government to ensure that the death penalty was not imposed on anyone suffering from mental disability.
PUCL president DR V Suresh said there is a danger of the death penalty being "used disproportionately against ethnic minorities, the poor or other disadvantaged groups".
"There is only one way to ensure such inequalities in the administration of justice do not occur: the complete abolition of the death penalty."
There have been protests against death penalty in India
In India the death penalty is carried out by hanging. An attempt to challenge this method failed in the Supreme Court, which stated in its 1983 judgement that hanging did not involve torture, barbarity, humiliation or degradation.
Under Indian law, the death penalty can be imposed for murder, gang robbery with murder, abetting the suicide of a child or insane person, waging war against the government, and abetting mutiny by a member of the armed forces.
In recent years, however, special courts have also extended the penalty to cases of terrorism under anti-terror legislation.
Some people are pushing for it to be used against rapists.
Last year, a former member of the Indian parliament, Anand Mohan, was sentenced to death for his role in a mob killing 13 years ago.
An Indian soldier was also sentenced to death for killing his superior in Indian-administered Kashmir last May.
The assassins of India's independence leader, Mahatma Gandhi, and former Prime Minister Indira Gandhi were among those executed in the past 60 years