A key adviser to former premier Kristina Keneally has told a corruption inquiry that a cabinet minute rejecting a proposal by a company linked to the Obeid family was rewritten to "completely reverse" its intent.
Tony Pooley, then deputy chief of staff to Mrs Keneally, told the Independent Commission Against Corruption on Friday he was "very surprised" the minute was resubmitted to cabinet in 2010 in a radically altered form.
The commission is investigating allegations the minute was doctored by Joe Tripodi and Tony Kelly, who were political allies of corrupt former Labor minister Eddie Obeid.
The altered minute recommended the government "proceed with direct negotiations" with infrastructure company Australian Water Holdings for a public-private partnership.
The inquiry has heard the Obeids could have made up to $60 million from the deal.
"It is exceptionally rare in my experience that a DPC [Department of Premier and Cabinet]-prepared minute is then changed ... to completely reverse the intent and recommendations of the minute," he said.
Mr Pooley said the Department of Premier and Cabinet and the state-owned Sydney Water were "vociferously opposed" to AWH's proposal.
"This was a strong, firm view that this was not a good minute," he said.
"It would be very unusual for a minute to come to cabinet where the two key agencies ... were both opposed to it.
"For that to be reversed almost in its entirety ... was highly unusual."
Mrs Keneally told the inquiry earlier this week that "this was the cabinet minute that wouldn't die - until I drove a stake through its heart".
The commission has heard allegations that Mr Obeid and Mr Tripodi agreed to oust former Labor premier Morris Iemma from the premiership in 2008 in return for a favourable deal for AWH.
Mr Iemma is expected to give evidence on Monday.
Liberal Senator Arthur Sinodinos, a former chairman of AWH, could give evidence as early as Wednesday.