"Mr Prime Minister, if this is not corruption, would you care to explain to the country what is corruption. It is a fit case for a court-monitored investigation," Congress spokesman Manish Tewari told reporters here.
The Supreme Court should take suo motu cognisance of the case and order an independent investigation, he said.
Claiming that certain "new facts" have emerged with regard to the issue, Tiwari said there is a "clear case of impropriety, a clear case of corruption and a definite case of conflict of interest".
Later, the ownership of the company changed and the state government came out with a notification, bringing down the restricted area from two-km to one-km around the sanctuary.
Also Read
Congress has been asking Modi to "come clean" on the issue and tell whether he was aware of the "clear conflict of interest" of the then Revenue Minister Anandiben Patel while allotting government land to the company allegedly having close business links with her daughter Anar Patel.
The party had on Saturday scaled up its demand for an SIT probe monitored by the Supreme Court, saying it should go into all allotments of government land when Modi was the Chief Minister. Congress has also demanded resignation of Anandiben who succeeded Modi as Chief Minister.