Mr Singh received a rapturous welcome on his return to India
An Indian man released from a Pakistani prison on Monday after spending 35 years on death row has admitted that he was a spy.
Kashmir Singh also criticised the Indian government which he said did nothing for him or his family while he was in jail.
He said he would not give details of his detention in case it jeopardised other Indians in jail in Pakistan.
He was sentenced to death in 1973, for spying in Pakistan.
'Not a penny'
"I did the duties assigned to me as a spy," Mr Singh said on Friday, the Press Trust of India (PTI) reports.
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"After my arrest... successive (Indian) governments did nothing for me," he told journalists in the city of Chandigarh. "The government after my arrest did not bother to spend a single penny for my family."
Mr Singh appeared reluctant to give many details about his imprisonment although he did say he had been chained up for 17 years of his detention.
His release was spearheaded by Ansar Burney, a social worker and cabinet minister who tracks people lost in Pakistan's jail system.
India and Pakistan have jailed hundreds of each other's soldiers and civilians during times of hostility.
Pakistani officials said that while Mr Singh's release was unconditional, they hoped it would lead to further prisoner exchanges.
'Hell on earth'
Ansar Burney discovered Mr Singh on a recent trip to a jail in Lahore and persuaded Pakistan President Pervez Musharraf to revoke his death sentence and order his release.
Mr Singh was a former policeman who had become a trader in electronic goods.
He was arrested in the city of Rawalpindi in 1973 and convicted of spying.
Pakistan and India frequently arrest each other's citizens, often accusing them of straying across the border - some are treated as spies.
Mr Burney is currently the government's caretaker minister for human rights.
Mr Burney said last week that Mr Singh had been held in a condemned prisoner's cell for most of the time since his conviction and had become mentally ill.
He said that he was first informed about the case several years ago by members of the Indian community in London.
But he was unable to locate Mr Singh, despite visiting more than 20 jails across the country in connection with his campaign for prison reforms and prisoners' rights.
The minister said Mr Singh had not received a single visitor or seen the open sky and, like other condemned prisoners, was locked in an overcrowded cell for more than 23 hours a day, in conditions which the minister described as "hell on Earth".