Controversial former Labor powerbroker Eddie Obeid will face three fresh corruption inquiries, starting at the end of this month.

But Fairfax Media can reveal that the Independent Commission Against Corruption plans a fourth inquiry into the Obeids' secret plan for a billion-dollar water deal. This inquiry, into Australian Water Holdings, is potentially more explosive than the Mount Penny coal exploration inquiry which found Mr Obeid's family had made $30 million, with the potential to make another $100 million.

The fourth inquiry, which will start early next year, will examine the Obeids' clandestine involvement in AWH, which manages hundreds of millions of dollars worth of work for Sydney Water.

It will look at former planning minister Tony Kelly's attempt to help the Obeids secure millions of dollars from a plan to have part of Sydney Water privatised and sold to AWH.