"I have explained so many times. 14 cases (mercy petition) were sent to the president during National Democratic Alliance (NDA) government and not even one was decided.
When my predecessor was in the office, he sent those 14 cases and 14 more cases, and two were decided," Chidambaram told reporters here.
"After I took over at the request of the president, all the cases are being reviewed and re-submitted one by one," he said.
The home minister said that the president had already passed orders in five or six cases.
"I think we have to follow some principle and some order. Every single case is being submitted in the serial order in which it appears on the list as it was earlier submitted to the president. And I think respect to the office of president requires that we accept they are submitted...and we await the president's decision," he added.
The Bharatiya Janata Party (BJP) Monday attacked the government for the delay in punishing Afzal Guru.
"The country wants to know about those responsible for the parliament attack. The government should punish them," Leader of Opposition in the Lok Sabha Sushma Swaraj said at a memorial service for the nine people killed in the attack.
On Dec 13, 2001, five heavily armed gunmen stormed the Parliament House and opened indiscriminate fire, killing nine people instantly.
The victims included five Delhi Police personnel, a woman Central Reserve Police Force (CRPF) trooper, two parliament watch and ward staff and a gardener. A journalist who was injured died later. All five terrorists were shot dead.
A year later, four accused, including Afzal Guru, who were arrested for the attack, were found guilty after a trial.
Guru, who is said to be a Jaish-e-Mohammed militant, was the only accused to be awarded the death penalty.