NEW DELHI: Anil Ambani, the billionaire chairman of India's Reliance ADA group, appeared Tuesday before a parliamentary panel investigating a multi-billion dollar telecoms graft scandal that has rocked the country's political and business establishment. Ambani testified days after police indicted officials and a unit of his group for conspiracy, cheating and other offences during a flawed 2008 telecoms licence grant process that may have lost the state up to $39 billion in revenue. The scandal is the largest of several corruption cases to have emerged in Prime Minister Manmohan Singh's second term. It has badly damaged the government's credibility and set off worries about regulatory risk in Asia's third largest economy. Police accuse Reliance Telecom, a unit of Reliance Communications , and three Reliance ADA officials, of conspiring to set up Swan Telecom as a front company to gain valuable radio spectrum. Indian rules bar an existing licence holder from owning more than 10 percent in another operator in the same market. Emerging from an hour-long questioning, Ambani did not speak to reporters. Two members of the committee told reporters that Ambani was questioned over grants of radio spectrum. Another member said Ambani told the committee he could not answer all their questions as the matter was in court. Ambani, one of India's highest profile businessmen, was questioned a day after tycoon Ratan Tata appeared before the same Public Accounts Committee. While the committee's recommendations are not binding on the government, the spectacle of some of India's biggest business names being questioned is almost unheard of in a country where leading industrialists have long been seen as untouchable. “This investigation has caused corporate India to sit up and take notice of the fact that there are law enforcement agencies in the country who are minded to ask tough questions if things get out of hand,” said Saurabh Mukherjea, head of equities at Mumbai-based Ambit Capital. “Even if the investigation comes to nothing from this point in, just the fact that we've seen our authorities being willing to ask India Inc tough questions will exert a degree of discipline on corporate behavior going forward.”