"We are in the process of looking forward and looking forward does not mean that our borders will be changed. We made it very clear that as far as we are concerned, the integrity and unity of India is non negotiable," Spokesperson in the External Affairs Ministry Syed Akbaruddin said.
He said the comment was "far from reality which takes us back into the past century".
"I will take back Kashmir, all of it, and I will not leave behind a single inch of it because, like the other provinces, it belongs to Pakistan," said the scion of highly influential Bhutto family.
When Bilawal made these remarks, he was flanked by former prime ministers Yousaf Raza Gilani and Raja Pervaiz Asharaf.
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Bilawal, who has announced plans to contest next general elections in 2018, heads the secular Pakistan People's Party which officially wants good ties with India.
Bilawal's father Asif Ali Zardari was Pakistan's president from 2008 to 2013.