The PM also said that "insinuation that the appointment was made to preempt the procedure recommended by the Select Committee is wholly unwarranted and devoid of any merit."
"I also refute the suggestion that the appointments to this post in the past by the UPA Government were motivated by collateral considerations," he said.
The Lokpal and Lokayukta Bills were still awaiting passage in the Rajya Sabha and it was referred to a Select Committee which has tabled its report today in the Rajya Sabha, Dr Singh said.
"Many changes have been suggested by the Select Committee which are required to be considered by the Government for introducing official amendments. After the Bill as amended is duly passed by the Rajya Sabha, it will be returned to the Lok Sabha for further consideration," he said.
The Prime Minister said even as the government was making all efforts to enact the new law, the top post in the CBI could not be kept vacant.
Accusing the government of trying to short-circuit the recommendations of a Parliamentary panel on the Lokpal bill to select the CBI Director, the Leaders of Opposition of Lok Sabha and Rajya Sabha, Sushma Swaraj and Arun Jaitely, had written to the Prime Minister earlier on Friday, asking him to put in abeyance the appointment of new CBI chief.
Both Ms Swaraj and Mr Jaitely had said that appointment of the new CBI Director should not have been done when the Rajya Sabha Select Committee had recommended that such appointments should be done through a collegium, that includes the PM as well as Leaders of Opposition among others. (Read Jaitley, Swaraj's letter to the PM)
Currently, the appointment is an administrative decision taken by a Cabinet committee, which has no Opposition representation.
The new chief was named just hours before the panel's recommendations were tabled in Rajya Sabha. The Lokpal is not yet an act of Parliament, since it has to be passed by it after the government tables a final version.
The government said that the decision to appoint the CBI Director was the Prime Minister's and he chose Ranjit Sinha from three eligible candidates. "The PM has the authority to decide, and he has (made the appointment) in his wisdom," Minister of State in the Prime Minister's Office V Narayansamy said.
The Congress too defended the decision. "It is not known when the Lokpal Bill will be passed, it could take months," party spokesperson Sandeep Dikshit said. "Appointments can't be kept on hold for this." He also said that the BJP was "polticising" every post in government.
The Lokpal Bill is yet to be debated and voted on in Lok Sabha and there are several parties that are opposed it in some form or the other.
Ranjit Sinha, a 1974-batch Indian Police Service (IPS) officer of the Bihar cadre and current Director General of Indo-Tibetan Border Force, has been named by the government as the next Director of the Central Bureau of Investigation (CBI). Mr Sinha will take charge from Amar Pratap Singh, who retires on November 30.