Jadhav, a former India naval officer, was awarded the death sentence by a Pakistani military court after he was declared a "spy" in that country.
"If Pak hangs Jadhav then India must recognise Balochistan as an independent country," he said in a tweet.
Speaking to reporters outside the Parliament, Swamy said it was useless to ask for consular access for Jadhav.
Noting that Pakistan targeted Jadhav after claiming he was creating problem in Blochistan, the MP said, "We must threaten Pakistan that if anything happens to Jadhav...we will consider Balochistan as independent nation and call Baloch representatives and ask them to form a government in exile."
BJP MP and former Home Secretary R K Singh underscored the need for adopting a policy of "strict reciprocity" with Pakistan.
He said a number of Pakistani nationals are arrested every month in India trying to carry out terror strikes and if New Delhi starts behaving the "same way, all of them will hang".
"International relations are carried out on the basis of reciprocity. And strict reciprocity, in my view, is the best course to adopt. In this (Jadhav's) case also, we need to adopt the course of strict reciprocity," Singh said.
He said Pakistan needs to understand that India arrests a number of their citizens every month with weapons.
"Pakistanis will come across to the Valley to carry out terrorist attacks with AK-47s, grenade launchers etc. They are put on trial, and in jails for 10-12 years and sent back.
"If this sort of thing (sentencing and executing Jadhav) happens and we (India) start behaving the same way, all of them will hang. We will set up a special court, we will change the law. Pakistan needs to keep this in mind," he said.
Pak army court sentenced Jadhav to death
Pakistan military court has sentenced Jadhav to death after he was convicted of "espionage and sabotage activities", prompting New Delhi to warn Islamabad that it is a case of "premeditated murder".
The trial proceedings that led to the capital punishment for Jadhav were also described by India as "farcical".
The award of the death sentence to the 46-year-old former Naval officer at a court-martial was confirmed by Pakistan's army chief Gen Qamar Javed Bajwa today and is expected to further deteriorate already strained Indo-Pak ties that were hit after the deadly attacks in Pathankot and Uri by Pakistan- based terrorists last year.
The court martial was closed to the public and consular access was not provided to Jadhav.