New Delhi, Dec 22 (IANS) Bharatiya Janata Party (BJP) leader Arun Jaitley Wednesday asked Prime Minister Manmohan Singh to quit if he was not ready to face a joint parliamentary probe into the spectrum scandal.

Addressing a public rally organised by the BJP-led National Democratic Alliance (NDA) here, Jaitley said only a Joint Parliamentary Committee (JPC) could find out why second generation spectrum was allotted at below the market prices in 2008.

The prime minister has said he was ready to face a Public Accounts Committee (PAC) to answer questions but he was against the formation of a JPC.

Jaitley, leader of the opposition in the Rajya Sabha, said this was unacceptable to the opposition, and the prime minister should quit if he did not want to face a JPC probe into the scandal.

Another BJP leader, Sushma Swaraj, was equally critical of the Congress and its multi-party government.

"Why are they afraid of JPC?" she thundered at the sprawling Ram Lila ground, where also present were leaders of the Janata Dal-United (JD-U) and Akali Dal among others.

She said four JPCs had been formed until now to probe various scandals, including two during previous Congress regimes.

"The (Niira) Radia tapes have exposed the stink in the executive, the legislature, the judiciary and the fourth estate, the four pillars of a democracy," she said.

"Neither the Supreme Court nor the PAC can answer the questions we are raising," she said. "If they have nothing to hide, why are they afraid of JPC?"

Business lobbyist Radia has been taped talking to industrialists, politicians and others suggesting that A. Raja should be made the communications minister in the Manmohan Singh government in 2004.

DMK leader Raja quit the cabinet last month in the wake of the scandal, which washed out parliament's entire winter session.