An NGO Friday alleged that over 75 percent of the funds of India's national political parties came from "unknown" sources.

According to the Association for Democratic Reforms, which works for good governance and transparency in politics, an analysis of the Income Tax returns and statements filed by parties with the Election Commission, showed that most of the sources of funding of six national political parties remain largely unknown.

Out of the total income of parties between 2004-05 to 2011-12 amounting to Rs.4,895 crore, as much as Rs.3,674 crore came from funds whose sources were unknown, it said.

The parties whose data was analysed included the Congress, Bharatiya Janata Party, Communist Party of India-Marxist, Communist Party of India, Bahujan Samaj Party and Nationalist Congress Party.

"Why can't the public get to know about the funding of parties when this is the practice in many countries including smaller ones like Nepal and Bhutan in our neighbourhood," asked Trilochan Sastry of the ADR.

"ADR recommends that full details of all donors should be made available for public scrutiny under the Right to Information," he said.