For four years since 2012-16, as many as 1,933 donations - amounting to Rs 384 crore - were not accompanied by PAN (Permanent Account Number) details. In the same period, 1,546 donations, amounting to Rs 355 cr, came without the donor's address.

Donations from unknown sources - without PAN or Aadhar details - amounting to Rs 159 crore, have gone to the BJP, the ADR said. In another report in January, the ADR said political parties receive most of their income from unknown sources.

Political parties got 60% of corporate donations in the financial year 2014-15, the report from the Association of Democratic Rights or ADR said today. Between 2012-16, corporate houses donated Rs 956.77 crore to five national parties, constituting 89 per cent of the total contribution from known sources.

Of the five big national parties -- BJP, Congress, NCP, CPI and CPM -- the BJP got the most donation, Rs 705.81 crore, from corporate donors. The Congress, in comparison, came a poor second with Rs 198 crore.

The CPI and CPI-M have received the lowest share of corporate donations -- at 4 per cent and 17 per cent.

The BSP was not considered for analysis in the report as the party has declared that it received no voluntary contributions above Rs 20,000 from any donor between 2012-13 and 2015-16.

In 2012-2013, the real estate industry was the biggest donor to political parties. For the next three financial years, manufacturing sector was the second biggest donor.

In the last decade, 83 per cent of Congress's income, amounting to Rs. 3,323.39 crore, and 65 per cent of BJP's income, amounting to Rs. 2,125.91 crore, had come from unknown sources, the ADR said in January.

Under the Income Tax Act, political parties don't have to pay income tax if they accept donations above Rs. 20,000 in cheque. For donations below Rs. 20,000, which can be given in cash, they are required to keep the donor's details.