The trio --- Shobha Karandlaje, GM Siddeshwara and PC Mohan --- has written letters to the union home minister, Lok Sabha speaker and top police officials in the state, seeking strict instructions to end this "pernicious practice".
"We have every reason to believe that the Karnataka government is misusing its position and tapping our mobile phones. This, according to us, is a clear violation of our fundamental right to privacy," said the letter.
Asked what led them to think that their phones were being tapped, Ms Karandlaje said "we got to know from agencies". Without specifying which agency, she added, "Many of our messages and information have been leaked".
With Karnataka throwing up a hung verdict, both the BJP and the JD(S) backed by the Congress had staked claim to form the government.
JD(S) leader Kumaraswamy has accused the BJP of approaching his lawmakers with offers of Rs 100 crores and Cabinet berths, allegations the BJP has rejected.
The BJP emerged the single largest party, winning 104 of the 222 seats for which polling was held, but is still eight short of majority. The JD(S)-Congress combine is well ahead of the halfway mark.
"Political situation is still fluid following a fractured mandate. The Congress government in Karnataka is taking advantage of the situation and has resorted to cheap tactics of tapping the telephones of BJP leaders," alleged BJP lawmakers in their letter.
According to law, any order to intercept phone calls and messages can be issued only by the union home secretary or his counterparts in states.
The Congress has dismissed the allegations, calling them "wild".
"When we have the numbers why should we be worried? They (BJP leaders) are the ones who are trying to do every dirty trick that is available in the book to try and form a government," said Dinesh Gundu Rao, working president of Karnataka Congress.