Colleagues of suspended Assistant Treasurer, Arthur Sinodinos, knew the very fact of his appearance before the independent commission against corruption to explain dodgy donations from an Obeid-linked company, would make his return to the ministry problematic.

But his performance once in the dock, described by one as "embarrassing", has only cemented those concerns.

Prime Minister Tony Abbott stood firmly by the embattled New South Wales senator when he stepped down last month pending questions over his knowledge (or ignorance as it turns out) of some $72,000 in political donations.

The money was paid by Australian Water Holdings of which he was chairman, to the NSW Division of the Liberal Party, of which he was a senior office holder and treasurer.