Raising the issue during Zero Hour, Saugata Roy said that a report of the Association of Democratic Reforms noted that an audit of the parties has revealed "a strange thing" that the income is mostly from unknown sources.
He said the Congress income in 2013-14 was Rs 598 crore while that of BJP was Rs 673 crore. While 83 per cent of the Congress income is from unknown sources, the percentage as regards BJP is 73 per cent.
Making a strong pitch for the parties to reveal the sources of income, he objected to CPI-M demand that his remarks be expunged.
He said the Election Commission has been time and again telling the political parties to bring transparency in their finances.