Karti said neither he nor his family were shareholders in any of the firms, while Chidambaram issued a statement saying "nothing was found in the fishing and roving enquiry" and he would like to see how far a "foolish government" will go in "harassing" his son.
Karti, in a statement issued in Chennai, said some officers of the investigating agencies visited his office on Wednesday.
"I was informed that they are investigating three firms of which two belong to my friends. They are owned by professionals and managed by competent board of directors. I am not aware of the third firm," he said.
"I made it clear to the officers what I had publicly stated earlier. Neither I nor any member of my family is a shareholder or director of any of the said firms. We do not have any economic interest in the said firms."
He said that as the allegation of his connection with the firms was "false".
He said there was no "basis for them to have visited by office or to make any enquiries in my office".
Chidambaram said: "As can be expected, nothing was found in the fishing and roving enquiry. I would like to see how far a foolish government will go in harassing him. I still believe that the department I left behind have many officers who will act according to their conscience."