"At least 2,234 Indians have contracted HIV while receiving blood transfusions in hospitals in the past 17 months alone, say officials.
Mr Khothari told the BBC that he was "shocked" by the revelation.
India has more than two million people living with HIV/Aids.
The highest number of patients who had been infected with HIV as a result of contaminated blood in hospitals, were from the northern state of Uttar Pradesh with 361 cases, Mr Kothari's RTI (Right to Information) query revealed.
The western states of Gujarat with 292 cases and Maharashtra with 276 cases rank second and third respectively.
The Indian capital Delhi is at number four with 264 cases.
"This is the official data, provided by the government-run Naco. I believe the real numbers would be double or triple that," Mr Kothari told the BBC.
Under law, it is mandatory for hospitals to screen donors and the donated blood for HIV, hepatitis B and C, malaria and other infections.
"But each such test costs 1,200 rupees ($18; £12) and most hospitals in India do not have the testing facilities. Even in a big city like Mumbai, only three private hospitals have HIV testing facilities. Even the largest government hospitals do not have the technology to screen blood for HIV," Mr Kothari said.
"This is a very serious matter and must be addressed urgently," he added."
May 31, 2016, "In India, Blood Transfusions Have Caused Thousands of HIV Infections," US News, Kimberly Leonard
"The data suggest screening procedures may not be adequate, though a government official says progress has been made."
"India is the second-most populous country in the world and has the third-highest number of HIV-infected people in the world – at around 2.1 million people – following South Africa and Nigeria." (end of article)