The $16.2 billion lease of Ausgrid is among the largest privatisations in Australian history, yet the NSW government is refusing to release details of the decision-making process beyond a one-page summary.

The refusal comes just months after the Auditor-General found the NSW government needed to be more transparent about the controversial "unsolicited proposals" process via which the Ausgrid deal was done.

Premier Mike Baird and Treasurer Gladys Berejiklian announced last month the government had accepted an unsolicited proposal from a consortium of local pension funds, meaning it did not go to tender.

The proposal by Australian Super and IFM Investors for the 99-year lease of 50.4 per cent of Ausgrid was revealed in late September.