RCP Singh said that the letter is the party's attempt to humiliate him.
Nitish Kumar is a man full of vendetta, former union minister RCP Singh told NDTV a day after he quit the Janata Dal (United) following snubs from the party boss. Mr Singh, who is also a former party president and was a close aide of Bihar Chief Minister Nitish Kumar, said that's why Mr Kumar "stooped so low and targeted his daughters".
The JDU had earlier demanded Mr Singh explain "irregularities" in properties linked to his daughters.
Nitish Kumar was reportedly upset with RCP Singh for his growing proximity to coalition partner Bharatiya Janata Party. Mr Singh had accepted a union cabinet berth without the party chief's consent. However, RCP Singh denies the charge, claiming Home Minister Amit Shah had spoken to Mr Kumar about cabinet expansion and offered one berth to the party on the condition that Mr Singh himself become a union minister. "It's a bare-faced lie," he said about accusations that he became a central minister on his own, without consulting with the party.
"Nitish Kumar asked me to go to Delhi and take oath as union minister," he told NDTV.
While resigning from the primary membership of the party, Mr Singh had said there was a conspiracy against him because he had become a union minister. "There's no cure to jealousy," he said in a jibe at Mr Kumar.
"Nitish Kumar will not become Prime Minister in any of his seven lives," he said, describing the JDU as a sinking ship.
A week after videos emerged of him raising slogans projecting himself as the future chief minister, JDU sought a reply from RCP Singh on all the properties he has acquired in the last nine years.
In a letter to Mr Singh, the party claimed that several irregularities had been noticed in properties that he had acquired.
Commenting on the letter, RCP Singh had told NDTV, "These properties were bought by my wife or daughters who are income taxpayers since 2010."
He said that the letter is the party's attempt to humiliate him and that Mr Kumar is "hitting below the belt".
After his resignation, RCP Singh has been staying at his native village in the Nalanda district and touring nearby areas in an apparent bid to find the ground under his feet.