"Sand mafia fund political parties...Sand mafia are the main source of RJD's funding...I would soon hold a press conference to make a big expose on Lalu Prasad's family's links with those big guns involved in sand mining," Modi told reporters here.
The senior BJP leader asserted that the state government was committed to take action against all types of persons involved in corruption.
In reply to a query as whether he had gone through the file of 'soil purchase', Modi tried to downplay the issue by saying that it was a very small issue.
"This (soil purchase scam) is a very small issue.
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RJD's Bihar unit spokesman and media in-charge Pragati Mehta dismissed the allegations as "baseless and absurd".
"We don't take notice of Sushil Kumar Modi's allegations. He has been in the habit of making baseless and absurd allegations against Lalu Prasadji and his family.....There is no force in his (Modi's) allegations," he said.
"BJP is the party of Ambani and Adani whereas ours is a party of poor people which is driven by workers' cooperation," Mehta added.
Kumar had in a blistering attack on Prasad yesterday said he had no option but to walk out of the Grand Alliance as he did not want to compromise with corruption.