An unkind observer might find it hard to imagine a bigger crisis for the scandal-prone NSW Parliament: its MPs have suddenly been left without a parliamentary ethics adviser.

In November the parliamentary ethics adviser, Ian Dickson, gave notice to Parliament of his retirement on December 31 after 13 years in the job.

But due to the rules for how his successor must be appointed, Mr Dickson is unlikely to be replaced until at least the end of next month, leaving the state's MPs to grapple with their consciences unassisted in the meantime.

The position was created in 1998 by then premier Bob Carr following a recommendation by the Legislative Council ethics committee.

Then treasurer Michael Egan described the job as being on hand to advise MPs ''on ethical issues concerning the exercise of his or her role as a member of Parliament (including the use of entitlements and potential conflicts of interest)''. The advice is treated confidentially and an annual report is issued outlining the number and types of issues broached but not by whom.