At a crowded press conference here, an angry Siddiqui levelled a spate of allegations against Mayawati saying he had enough material to cause an "earthquake".
He also claimed that there was a threat to his life.
Siddiqui played six audio clippings of his phone conversations with Mayawati to support his allegation that money had been demanded from him.
Siddiqui claimed he had 150 such recordings.
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Accusing Mayawati of having referred to "bearded Muslims as dogs", Naseemuddin said he had objected to the remark.
At a hurriedly convened press conference Mayawati soon hit back.
"Expelled BSP leader Naseemuddin Siddiqui is a big black mailer and earns money through it...People have complained about it. And it has been proved right today," she said.
Mayawati said she had received complaints about Siddiqui from party workers.
"One who can tape BSP national president's conversations cannot be called a devoted and loyal worker....But he will not be able to blackmail me as what I say in private is what I say in public," she asserted.
Mayawati claimed that when some workers were asked about the deposit of party's membership drive and they said the amount had been given to Siddiqui.
"I warned that if he cannot give proper account, he will have to pay it himself....I will not allow him to usurp party money which belongs to the poor and deprived through which we run the party...I do not want your property money...I simply want the account of poor peoples' money," she said.
"Muslims have faith in me that I cannot betray them...It is from the Muslims that we received maximum calls after his expulsion as he was not letting them progress in the party."
On Naseemuddin saying that his 8 year old daughter died while he was busy in Mayawati's election in Bilsi, the BSP supremo said this was it was for the first time she had heard of her.
He (Siddiqui) had always mentioned that he had only two sons, she said.
"When Mishra came to BSP, Naseemuddin was very perturbed...He (Mishra) is working with full devotion and gives me more respect than his real sisters...He has been with me through all my problems and has not taken a single paisa for the cases he contested for the party," she said.
Earlier, Siddiqui had alleged that "BSP is being knowingly weakened by Mayawati and Anand Kumar (her brother) as part of a conspiracy by Satish Mishra and company"
Siddiqui claimed that the BSP was totally under the grip of Mishra and company and that Mayawati was being blackmailed by them.
"I know her more than anyone else...If I give the proof against Mayawati, Anand and Mishra it will be a big 'tamasha'," he said.
However, Mayawati sought to demolish all his allegations.
She alleged that people had told her that Naseemuddin had taken money from business houses promising to do their work once BSP came to power in the state.
Everyone can progress in life, Mayawati said.
"BSP workers say ever since I made my younger brother vice president, he (Naseemuddin) was very perturbed as he used to claim he was number two in the party...I had to bring my brother in the party as we need honest people not selfish ones. It was out of compulsion that I had to bring him," she said.
He also claimed that during a meeting on April 19 Mayawati had tried to belittle Kanshi Ram by comparing party's showing in Uttar Pradesh and Punjab Assembly polls.
Trashing all allegations, Mayawati said she had been warned about Siddiqui by Kanshi Ram himself, who used to say that he might prove to be a hurdle for the BSP.
Yesterday, BSP had expelled Siddiqui, its most prominent Muslim face, and his son from the party for carrying out "anti-party" activities.
The war of words gave the ruling BJP a chance to take potshots at the BSP chief, saying it was high time for Mayawati to quit politics.
"Mayawati does politics just for her own sake and has lust for money and nothing else. After today's expose, she should quit politics," BJP spokesman Chandra Mohan said.
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