Singh, who is in charge of party affairs in Karnataka, however, denied reports that he had asked the Chief Minister to order an inquiry into the matter.
"The whole thing is totally transparent. It was the lowest tender by the company. The file never came to the Chief Minister. I have not asked for an inquiry.
"I have only advised that he withdraws. It is not an order, but an advice. Legally, the son does not have to quit. As a (matter of) propriety, he may," Singh told PTI when asked whether he had asked the Chief Minister to ensure that his son resigns from the company.
Karnataka is among the handful of states run by Congress which lost power at the Centre two years ago.