"Safety and security of Pakistan's nuclear arsenal is of a major concern. The growing radicalisation within the military, given attacks on its own internal bases, could lead to these nuclear weapons being hijacked by radical Islamists," said Pervez Hoodbhoy, who was here for the London launch of his book 'Confronting the Bomb'.
The nuclear physicist and defence analyst estimated Pakistan's arsenal to be similar to India's, at around 120-130 warheads.
He was answering questions from members of the Indian Journalists' Association at the Indali Lounge here last evening.
"Earlier, such weapons were seen just as a means of deterrence. The most dangerous development is the increasing search for fissile material as a new dimension of tactical nuclear war has entered the picture. This means the number of weapons will steadily increase," he said.
Hoodbhoy, who received his PhD in nuclear physics from Massachusetts Institute of Technology (MIT), stressed that the issue needs to be addressed for the sake of sub-continental as well as global security.
"India and Pakistan have come close to nuclear war at least five times in 1987, 1990, during Kargil (1999), after the attack on the Indian Parliament (2001) and the Mumbai attacks in 2008.
Given the history of nuclear tension, we can't afford to be passive on this issue. The fallout, from the blast itself to the radioactive effects, will be felt not just in the sub-continent but around the world," he said.
"Confronting the Bomb: Pakistani & Indian Scientists Speak Out", published by Oxford University Press and edited by Hoodbhoy, is a compilation of essays by scientists from both sides of the border.
It kicks off with the atomic age in India in 1974, followed by Pakistan and traces the furious nuclear race after the 1998 nuclear tests.
"Pakistan started developing its nuclear weapons only because India embarked on it. India has remained primary enemy. But to some extent that perception is changing, with Gen Kayani [Chief of Pakistani Army Staff] recently saying that Pakistan's major challenge is the enemy within.
So there seems to be a doctrinal shift within the army but Kayani himself is under attack within the forces," said Hoodbhoy, who admits receiving threats against his own life.
"Jihadists still operate within Pakistan and the state's policy regarding Islamists has been a confused one," added Hoodbhoy, a visiting professor in the physics department at Lahore University of Management Sciences (LUMS)
He is known for speaking out against the Pak's nuclear establishment.
He is now even sceptical of the peaceful uses of nuclear technology in India and Pakistan.
"Whether electricity generated from nuclear sources is really efficient is a big question mark.
"The construction of nuclear reactors is very expensive and should an accident similar to Japan's Fukushima disaster in 2011 were to occur in India or Pakistan, both countries may not have the capacity to deal with it the same way," he added.