A shortage of HIV/AIDS drugs provided under the government's free medicine program, after some drug makers halted supplies due to delayed payments, has left thousands of patients in India without treatment.

The country's National AIDS Control Organization, which is part of the healthcare ministry, acquires antiretroviral drugs for treating HIV/AIDS from companies through a bidding process and then supplies the drugs to healthcare providers across the country, said a report by Reuters

Some drugmakers stopped participating in the bidding over the last year because of payment delays, which resulted in a drug shortage, said Leena Menghaney, an activist with the medical charity Medicins Sans Frontieres.

At the end of 2013, India had the third-largest number of people living with HIV in the world, accounting for about 4 out of 10 people living with HIV in the Asian region, according to the United Nations' AIDS program.

"The supply chain has broken down, tenders have not been filled. As a result there are not enough drugs in the program to meet the needs of the people. Patients have been told to fend for themselves," Menghaney told Reuters. "No manufacturer who supplies to the national program, where the margins are miniscule, should have to be faced with payment delays. But the way to deal with that is not to boycott the program."

NACO officials in New Delhi could not be reached for comment.

A trust that works with HIV/AIDS patients, Delhi Network of Positive People, said it plans to file a lawsuit against the government over the shortage of the life-saving drugs in various states, said the group's president, Vikas Ahuja.

India has provided free antiretroviral drugs for HIV treatment since 2004, but only 50 percent of those eligible for the treatment ended up getting it in 2012, a World Health Organization report asserted last year.