He also hit out at the RJD for questioning his silence after the TDP pulled out of the NDA seeking similar benefits for Andhra Pradesh.
Mr Kumar declined to comment on the fresh conviction of RJD supremo Lalu Prasad in the fourth fodder scam case but said the claims of the former chief minister and his family members of being "framed" in corruption cases "could convince only hardcore supporters".
"I had written to the then prime minister for a special status to Bihar in 2005, shortly after assuming power in the state. A year later, we got a resolution passed in the state assembly to the effect.
"Since then, the demand has been raised by us relentlessly and I have not strayed for even a second. I'm amused to see those who were never concerned about the issue have suddenly started questioning my silence," Mr Kumar told reporters at party headquarters in Patna.
He also indicated that the issue of special status for Bihar would be raised before the 15th Finance Commission.
Mr Kumar, who is the JDU national chief, had made a surprise appearance at a press conference convened by state chief Bashishth Narain Singh to announce merger of a breakaway faction of Hindustani Awam Morcha (Secular) founded by former chief minister Jitan Ram Manjhi.
Senior JDU leader and state minister Rajiv Ranjan Singh was also present on the occasion.
Mr Kumar was responding to queries about the relentless attacks by Lalu Prasad Yadav and Leader of Opposition in state Assembly Tejashwi Yadav.
They have been challenging him to speak up on the issue of special status for Bihar in the backdrop of the TDP walking out of the NDA over a similar demand for Andhra Pradesh.
"Special status is a need for Bihar. We will work towards ensuring that it is fulfilled. But we are not going to issue statements about the matter every now and then. We have always placed interests of the voters above their votes, unlike our detractors," he said.
About Mr Yadav's conviction in the Dumka treasury case, Mr Kumar said, "It is a judicial verdict and I have never spoken about a judgement passed by a court of law."