In his communication, Digvijay Singh urged the Prime Minister to ask the Ministry of Corporate Affairs to institute an inquiry by the Serious Fraud Investigation Office (SFIO) into the matter, saying that, "a prima facie case does exist".
He was referring to reports related to the association of BJP chief with a Nagpur-based company Purti Power and Sugar Limited, regarding which "irregularities" have come to the fore.
"Gadkari has also said that he is open to a free and fair investigation. Being the National President of BJP, it is in the fitness of things that his case is properly investigated and he gets a fair opportunity to prove his innocence and clear his name," Singh said.
It is for the first time that any Congress leader has demanded a probe into the issue.
The Party has so far been maintaining that there should not be any politics on the private business of individuals and unless some investigating agency stumbles upon any irregularity, there is no need for Congress to target the BJP chief.
Singh has also attached with the letter a report compiled from information taken from the official site of the Ministry of Corporate Affairs and said that findings of a TV investigation as well as this report make "some very pertinent points that requires serious attention."
