"The police commissioner is not telling the media that the FBI found the presence of heart arrest injectable poison lidocaine in Sunanda’s body," Swamy tweeted.
After receiving the observations by the All India Institute of Medical Science in Pushkar's viscera report, Bassi on Friday confirmed that her death was due to 'unnatural' causes.
Speaking to the media, he asserted that in the report by the Federal Bureau of Investigation, it was said that none of the samples sent to them contained any radioactive material.
According to the AIIMS panel, which is headed by Sudhir Gupta, the head of the Department of Forensics, Pushkar died after being poisoned by Polonimum-210 or Po-210, sources state.
The Delhi police had submitted a 15-page FBI report to AIIMS medical board for further opinion.
Sunanda Pushkar, 51, was found dead at the Leela Hotel in New Delhi in January 2014.
Pushkar's viscera samples were sent to the FBI lab in Washington in February last year after a panel of doctors from AIIMS said that the alleged 'poison' could not be detected in Indian labs.