The former Tamil Nadu chief minister also appealed President Pranab Mukherjee not to grant approval to the ordinance.
Karunanidhi recalled that BJP as an opposition party had strongly opposed the insurance reforms and argued that there won't be any assurance that the investing firms will not take back the money in the event of a crisis.
Having passed the Bill in Lok Sabha with majority, the government opted for ordinance since it lacked adequate numbers in the Upper House, he said in a statement here.
While the Insurance Bill was taken up by a Select Committee after which it was tabled in Rajya Sabha, no discussion had taken place on it, the DMK chief said adding an ordinance in such a situation would amount to violating the "sanctity of Parliament."
The Bill seeks to increase FDI cap in insurance sector from the current 26 to 46 per cent.
The DMK president said many of India's public sector undertakings were dependent and confident about funding from PSU insurance companies and wondered why government was desperate to promote FDI in the sector.