Terming it as a "serious issue", Advani said had it been a small matter, Pranab Mukherjee would not have complained to Singh in this regard.
"I had publicly said in Parliament that if Pranab Mukherjee would not have been there in the government, I wonder how it would function. He is an intelligent person and hence I consider this a serious issue," he told a BJP rally here.
The senior BJP leader said the NDA will raise the issue in Parliament during the forthcoming Monsoon session.
Advani maintained that in his letter Mukherjee had asked the Prime Minister for a "secret investigation" into the suspected bugging of his office, indicating that this was a serious matter.
"There were adhesives found in 16 places but they said it was chewing gum. A small kid can come and paste chewing gum maybe in one or two places, but will he paste it in 16 places?" Advani asked.
The BJP Parliamentary Party chief did not spare the Prime Minister while taking digs at Mukherjee.
"The Prime Minister's case is different but I consider Pranab Mukherjee as being very intelligent. Hence, he should also consider the people of the country as intelligent. He should understand that the explanation given by those investigating that it was chewing gum will not be swallowed by anybody. Nobody will accept it," Advani said.
He insisted that the Prime Minister should place the whole truth behind this "shameful act".