The Indian parliament has moved a step closer to banning domestic firms from manufacturing low-cost generic copies of patented drugs.
Many rely on cheap copies of drugs
Campaigners say the move will deprive millions of people around the world of access to cheap life-saving medicines.
The bill will ensure India meets World Trade Organisation (WTO) rules.
It has been approved by the parliament's lower house, but must still be sanctioned by the upper chamber before it becomes law.
The new legislation will replace the current patent law, which has allowed drug makers to copy patented drugs as long as they use a different manufacturing process.
This liberal approach has helped to foster a strong drug manufacturing industry in India for more than three decades.
However, the government argues that patent recognition is an essential pre-condition for India's drug industry to further its own drug research and development or attract foreign partners.
Health activists have urged the Indian Goverment to rethink its proposals, claiming that they would see millions of Aids patients miss out on cheap medication.
Ellen't Hoen, of the relief agency Medecins Sans Frontieres, said: "Fifty percent of people with Aids in the developing world depend on generic drugs from India"
"The patent law will cut the lifeline to other countries."
The 545-member lower house passed the Patent (Amendment) Bill following a walk out by members of the Hindu nationalist opposition.
They argued the legislation was a "sell-out" to global drug firms.
The Hindu nationalist Bharatiya Janata Party (BJP) warned if passed the legislation would trigger a massive increase in the price of patented drugs.
BJP leader V.K. Malhotra said: "The government will be now responsible for the consequences of the bill and the hardships that will heap upon the people."
Speaker Somnath Chatterjee called for a vote after the Congress party-led coalition government pledged safeguards to prevent a hike in prices of crucial pharmaceutical products in India.
Commerce Miniter Kamal Nath said: "The government will have enormous powers to deal with any unusual price rise."
The vote went the way of the government after its Communist allies dropped their oppostion to the bill following concessions.