NEW DELHI (Reuters) - Indian opposition parties demanded a probe on Thursday into allegations of wrongdoing by the Adani Group and said they would raise the issue in parliament after its chair Gautam Adani was charged in the U.S. over an alleged bribery scheme.

Billionaire Adani was indicted by U.S. prosecutors for his alleged role in a $265 million bribery and fraud scheme and arrest warrants were issued for him and his nephew, plunging his conglomerate deep into crisis for the second time in two years.

The Adani Group rejected the allegations as baseless and said it complied fully with all laws.

Adani has been the target of Indian opposition parties who say that he and his conglomerate have been protected by Prime Minister Narendra Modi's government, charges both deny.

Modi's opponents say he has longstanding ties with Adani, going back nearly two decades to when Modi was chief minister of the western state of Gujarat, to which Adani also belongs.

They accuse the government of favouring the group in business deals, charges the government has rejected as "wild allegations".

"We are raising this issue, it is my responsibility to raise this issue as leader of opposition," Rahul Gandhi, leader of the main opposition Congress party, told reporters when asked if he would bring it up in parliament next week.

Gandhi has led the opposition attack against Modi for what he says are Modi's links to Adani since U.S. short-seller Hindenburg Research issued a report last year accusing the Adani group of using offshore tax havens improperly - which the company has denied.

Congress president Mallikarjun Kharge called for a comprehensive parliamentary probe into "every aspect of the working of the Adani Group".

Sanjay Singh, a lawmaker from the opposition Aam Aadmi Party, said the indictment was a serious matter.

"All pending matters against Adani should be probed by an investigation agency and monitored by the Supreme Court," Singh said.

There was no immediate response to the indictment from the Indian government.

However, Amit Malviya, a leader of Modi's Bharatiya Janata Party and its IT cell head, said Congress should not get "needlessly excited".

"The document you quote says, 'The charges in the indictment are allegations and the defendants are presumed innocent unless and until proven guilty'," he said in response to a post by Congress spokesman Jairam Ramesh seeking a parliamentary probe.

"The timing of the report, just before the parliament session and Donal(d) Trump's impending presidency raises several questions," he said, without elaborating.