Sethna said that Kalam had no authority to criticise former DRDO scientist K Santhanam's claims that Pokhran II test was a failure.
Sethna said, "What did he (Kalam) know about extracting, making explosive grade? He didn't know a thing. By being a president he appeared to wear the stature. He relied on atomic energy to gain additional stature."
He also advised politicians not to interfere in scientific matters.
Earlier on Aug 27, Kalam had claimed that Pokhran II nuclear tests were a success rubbishing Santhanam's claim that tests were not successful.
Kalam, who mentored India's nuclear programme, said the only thermonuclear device (hydrogen bomb) tested in 1998 produced the "desired yield".
Earlier, Santhanam, who coordinated the Pokhran II tests, had claimed that the only thermonuclear device tested was a "fizzle".