Drought-hit farmers in northern India are resorting to selling their wives to repay debts to local loan sharks, activists say, as one of the weakest monsoons in years takes its toll.

Poverty, poor administration and a lack of education means farmers in the rugged Bundelkhand region are taking extreme steps to pull through a poor rainy season, they say.

"This has been happening for quite some time now, but people were hesitant to come out with all this," said Manoj Kumar, a social activist working with farmers in the area.

Excluded from the formal banking sector, the poverty-stricken farmers often turn to usurious private money lenders when banks refuse them loans or even accounts.

After five years of poor crop yields and steadily decreasing rainfall, the crushing weight of the high interest payments has led to a well-documented spate of suicides and increasing cases of human-trafficking.

Another social worker, Shailendra Sagar, said the situation of farmers in Bundelkhand, a region that spans the states of Uttar Pradesh and Madhya Pradesh, was "pathetic".

"They are living in debt. Selling off one's wife or daughters is the last resort," he said.

The sale price for married women is hard to ascertain and their fate after being sold is equally difficult to follow.

Local reports have suggested wives can be pawned or sold for anything between one rupee to 12,000 rupees ($240).

Some women are sold under the guise of a legal marriage, complete with a formal contract, but activists believe others end up being exploited by prostitution rings.

In the last four to five years around 50 per cent of the region's population has left Bundelkhand villages to find work in cities, and at least 500 farmers have committed suicide, according to various Indian media reports.

For India's 235 million farmers, a bad monsoon can spell financial disaster because of the lack of irrigation.

Low rains have ravaged India's rice, cane sugar and groundnut crops, and have disrupted the flow of water into the main reservoirs that are vital for hydropower generation and winter irrigation.

About 40 per cent of India's districts have declared a drought, and the India Meteorological Department this week said the country faced a 20 per cent annual rainfall deficiency, though that figure is expected to improve with recent patchy rains. Ranjana Kumari, director of the Centre for Social Research in New Delhi, said research had identified Bundelkhand as one of the regions most vulnerable to sex trafficking.