India's most populous state will drop legal proceedings against farmers accused of burning crop waste, a major source of pollution, as the ruling Bharatiya Janata Party tries to placate growers ahead of elections next year to the state assembly.

The action comes at a time when some states have stepped up punishments for crop residue burning to avert an expected spike in air pollution that brings smog every year during the low temperatures of winter.

The predominantly agricultural northern state of Uttar Pradesh, which is home to more people than Brazil, is also considering waiving fines imposed on farmers, an influential voting bloc, for burning crop stubble.

"The idea was not to punish farmers but to spread awareness about crop stubble burning and its effect on the environment," Navneet Sehgal, the top official in the state's information department, told Reuters.

Shiv Kant Dixit, chief of the Bharatiya Kisan Sangh, or Indian Farmers' Federation affiliated to Prime Minister Narendra Modi's BJP, said it had urged the state to withdraw legal cases against farmers for crop residue burning.

"About 10,000 farmers have been slapped with cases for stubble burning, and a fine of about 1 billion rupees was imposed," Dixit said, referring to a total figure equivalent to $13 million.

The Uttar Pradesh government is looking to mollify angry farmers ahead of the state assembly election, said Sudhir Panwar, the chief of a farmers' group, Kisan Jagriti Manch.

For more than eight months, tens of thousands of farmers have camped on major highways to the capital, New Delhi to oppose new farm laws, in the longest-running growers' protest against Modi's government. 

The election in Uttar Pradesh, which sends 80 lawmakers, or more than any other state, to parliament in New Delhi, is often seen as a barometer of the popularity of the federal government.

Modi's BJP is expected to pull out all the stops to hold on to the state, which has a population of 240 million.