More than 50 per cent of the funds national parties received during the financial year 2017-18 came from "unknown" sources that included donations through electoral bonds and voluntary contributions, according to election watchdog Association for Democratic Reforms (ADR).
According to it, the total income of BJP, Congress, CPI, BSP, TMC, and NCP in 2017-18 was Rs 1293.05 crore.
The income of these parties from "unknown" sources was Rs 689.44 crore, which is 53 per cent of their total income.
Out of the Rs 689.44 crore, the share from electoral bonds was Rs 215 crore or 31 per cent, the report said.
The parties received Rs 354.22 crore or more than 51 per cent of the fund from unknown sources through voluntary contributions (below Rs 20,000), it said, adding the total income from other miscellaneous unknown sources was Rs 4.5 crore.
Thirty-six per cent of their income or Rs 467.13 crore from "known" donors, whose details were available from contribution reports submitted to the Election Commission.
They got Rs 136.48 crore from other known sources, such as from the sale of assets and publications, membership fees, bank interest, and party levy, the report said.
According to donation reports (containing details of donations above Rs 20,000), only Rs 16.80 lakh was given in cash to the national parties.
The CPI(M), which is also a national party, was not included in the analysis as its "schedules or annexures were unavailable for the financial year 2017-18".
At present, political parties are not required to declare the names of individuals and organisations giving less than Rs. 20,000 nor of those who donate via electoral bonds.
While the national parties were brought under the Right to Information Act by the CIC ruling in June 2013, they have still not complied with the decision.