"Whoever is making such an allegation, he, in this case (former minister R) Ashok, should prove it if he has any evidence. Yes, it is a very serious matter," Karnataka Congress president G Parameshwara told reporters here.
Siddaramaiah had yesterday rejected the allegation levelled by Ashok recently that the phones of BJP and JD(S) leaders in the state were being tapped.
The chief minister had also alleged that it was the BJP- led central government which had been tapping the phones of Congress leaders.
"The chief minister must have some information, since he also heads the intelligence wing," he added.
State Home Minister Ramalinga Reddy had also dismissed the BJP's charge and hit out at the Centre, alleging that it was not only tapping "our phone calls", but also "misusing" agencies like the CBI to harass Congress leaders.