New Delhi, Oct 18 (IANS): Prime Minister Manmohan Singh has nothing to hide in the allocation of coal blocks and the CBI, which is investigating the matter, could ask him questions, Parliamentary Affairs Minister Kamal Nath said Friday.

"The PM is a citizen of the country, the law applies to him equally. If the CBI believes it is going to assist their investigation, they can ask him some questions, he will certainly reply," Kamal Nath said.

"He has nothing to hide, he is not above the law," Kamal Nath said in an interview to a TV news channel.

Defending the prime minister, Kamal Nath said ministers sign files overseen by bureaucrats, and may not be aware of all the details of the file.

"There are so many files that have come to me, I cannot even remember. They (bureaucrats) are supposed to have gone through them... That is the system. How does the government function? Did the prime minister say give the charge to Birla? No, he did not. He just happened to be the coal minister at the time," Kamal Nath said.

The Central Bureau of Investigation (CBI) has filed a first information report (FIR) against former coal secretary P.C. Parakh and industrialist Kumar Mangalam Birla for alleged irregularities and criminal conspiracy in the allocation of two coal blocks in Odisha.

Parakh, however, said it was Prime Minister Manmohan Singh who decided on the allocation of the two coal blocks in 2005.

Following this, the Bharatiya Janata Party (BJP) has been asking the prime minister to own responsibility for the allocation.