Sarabjit's sister Dalbir Kaur told reporters here that Pakistan President Asif Ali Zardari should show magnanimity by releasing her brother.
"He should show 'bada dil' (large heart)," she said.
The 49-year-old Sarabjit was sentenced to death for alleged involvement in a string of bombing in Pakistan in 1990.
It was very unfortunate that Pakistan announced the decision to release in June this year and then did a U-turn and released another prisoner (Surjit Singh), she said.
If former Prime Minister Indira Gandhi and Pakistan's former Prime Minister Benazir Bhutto had been alive, Sarabjit would have been freed by now, she said.
But giving credit to Indian government, she said it had made a lot of efforts and even (Congress leader) Rahul Gandhi had assured her that Sarabjit would be released.
"I am sure Zardari would not let any harm come to Sarabjit and would release him, notwithstanding pressure from hardliners. It is a must for building good relations between the two countries," she said.
Sarabjit's daughters Shapan and Poonam were also present on this occasion.
The campaign aims to collect one lakh signatures, to be submitted to Pakistan High Commission in Delhi.