"The minister himself has said the reports are speculative... How can we comment on it," Rijiju said when he was asked if the home ministry would probe the bugging reports.
"There is nothing concrete in it," the minister said.
Media reports Sunday said bugging devices were found at Gadkari's Delhi residence.
This was however denied by Gadkari and those close to him.
"Reports in a section of the media about listening devices having been found at my New Delhi residence are highly speculative," Gadkari tweeted.
Congress demanded a probe into the allegations, with former prime minister Manmohan Singh saying it is not a "good omen".
"If ministers' houses are bugged, then it is not a good omen. It should be investigated. How can it happen? It should be explained by the government in the house," the former prime minister told reporters at an Iftar get-together hosted by Congress president Sonia Gandhi.