The NSW opposition claims Premier Barry O'Farrell is trying to protect Pru Goward by saying lower house ministers need not attend an inquiry into ministerial conduct.
Mr O'Farrell mocked the opposition's establishment of the Legislative Council Committee on Ministerial Propriety during question time on Thursday.
While he said he expects himself or any current or former minister in the upper house chamber to front the inquiry if requested, he did not propose any minister of the Legislative Assembly attend.
That was depicted by the opposition as a damning assessment of the Family and Community Services Minister by her leader given that the committee's first hearing planned to focus on "misleading statements" made by Ms Goward to parliament.
"This is an absolute vote of no confidence by the premier in minister Goward," Opposition Leader John Robertson said in a statement.
"By blocking minister Goward from fronting this inquiry, the premier is breaking the standards he set for himself and his ministers."
The committee was announced last month and will look into ministerial responsibility, potential conflicts of interest between a minister's public and private interests, the influence of lobbying and the lobbyist code of conduct.
But Mr O'Farrell said lower house ministers were already under scrutiny.
"Every day that parliament sits, ministers face the scrutiny faced in question time," he said to jeers from the opposition.