The Supreme Court was moved Tuesday for a CBI probe to ascertain the alleged role of four top bureaucrats and Congress president Sonia Gandhi in the coal blocks allocation scam.

Petitioner M. L.Sharma in his PIL sought a Central Bureau of Investigation (CBI) probe against T.K.A. Nair, the then principal secretary to then prime minister Manmohan Singh, former power secretaries V.S.Sampath and H.S.Brahama, former home secretary R.K.Singh and Sonia Gandhi to ascertain their role in coal blocks allocation and acquisition of tribal land.

Sampath, presently the chief election commissioner, was power secretary in 2008 and was succeeded by Brahama, now one of the two election commissioners, in 2009. R.K.Singh is now a BJP Lok Sabha member from Bihar.

The PIL petitioner has also sought direction to the CBI to file before the court the photocopy of the diary, seized from industrialist Kumar Mangalam Birla's office, that allegedly contains the "names of several politicians to whom large cash amount has been paid".

Sharma in his application said that CBI wanted to question Nair to understand the role of the prime minister's office in the allocation of the coal blocks between 2006 to 2009 - a period when then prime minister Manmohan Singh was holding charge of the coal ministry.

The investigating agency approached the department of personnel and training in July 2013 for its nod to question Nair, Sampath and Brahama but permission was refused and the same was communicated to the apex court Sep 10, 2013.

Referring to Sanjaya Baru's book about his days in PMO as media adviser to Manmohan Singh, Sharma in his application said the facts revealed in the book state that all "files from PMO used to go to Congress president Sonia Gandhi for final decision and direction".

The application is likely to be taken up for hearing on July 8 when the coal blocks allocation matter will come up for hearing.