India's main opposition Bharatiya Janata Party (BJP) accepted a $2,500 donation from Dow Chemical, government documents have revealed.
Dow Chemical is the American firm which bought the controversial company Union Carbide in 2001.
A gas leak from the Union Carbide plant in the central Indian city of Bhopal in 1984 killed nearly 3,000 people.
There have been at least 15,000 related deaths since. Survivors still suffer from chronic respiratory illnesses.
The leak of tonnes of methyl isocyanate gas from the plant in Bhopal owned by Union Carbide, now a subsidiary of Dow Chemical, is considered one of the world's worst environmental disasters.
The information was revealed by the Election Commission of India after a freedom of information request on the funding of political parties and donations received by them between 2005 and 2007.
Senior BJP leaders said they would check party records before commenting.
Dow Chemical said the donation had been a one-off and broke no rules.
"It is a common practice in several democratic countries to give donations to political parties which is legal," a company spokesman said.
"Dow Chemical International Private Ltd made one such legal donation to the BJP in India. We have made no other political contribution."
Senior BJP leaders have often accused the Congress party of not taking action against those responsible for the gas leak.
Campaigners want legal action pursued against Union Carbide and Dow Chemicals and are angry that the BJP accepted the donation.
"Dow Chemicals, one of the biggest chemical companies globally, acquired a controversial firm like Union Carbide. Accepting a donation from them cannot be justified," Gopal Krishna of the Delhi-based research group ToxicsWatch said.
"It is a serious matter. If a political party behaves in this fashion, then they should be exposed," he said.
Political parties in India accept donations from individuals as well as from companies and industries.
But it is rare for a mainstream party to accept money from a firm which is mired in controversy.
By Panini Anand
BBC Hindi service
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