The water authority had claimed legal privilege over the memo, which was sent from general manager Kevin Young to senior staff in the office of then water utilities minister David Campbell on September 29, 2006.

Retired judge Sir Laurence Street, who was commissioned by the upper house of Parliament, the Legislative Council, dismissed the privilege claim, saying the public interest outweighed the commercial concerns and recommended it be made public.

That advice was given last January 20 but the memo was not released and Sir Laurence's recommendation was kept secret until Wednesday night, when the Greens won a motion to have it released.

It came in a tumultuous night for the Government in which the Shooters Party voted against Labor on pieces of legislation and motions put by other parties.

John Kaye, of the Greens, said the Government's decision to stop Parliament a day early, adjourning to September, had stopped the further release of the memo.

"The Government has shut down Parliament to avoid a number of embarrassing outcomes, one of which would be us getting the documents on Tillegra," Mr Kaye said.

The memo was among a box of documents produced in the upper house but not made public, because of the privilege claim.

Sir Laurence concluded the memo should be released in order to contribute to an informed public debate about any need for Tillegra Dam.

Mr Kaye said it fell to Mr Young to say why the memo should not be released.

Mr Young said yesterday his hands were tied.

"Hunter Water must respect the processes of parliamentary privilege, so at this stage I am unable to comment," he said.

"As I always am, I would be happy to comment once the parliamentary process is concluded."