The NSW Greens' supreme decision-making body is being asked to consider the integrity of the ballot which saw Dawn Walker preselected to fill a seat in the upper house, opening the way for a push to overturn the result amid escalating factional tensions.

In December Ms Walker won the ballot to replace retiring upper house member Jan Barham by just 13 votes over Kelly Marks, a former staff member in the office of the late Greens MLC John Kaye.

Dawn Walker won the ballot to replace retiring upper house member Jan Barham in December.

But the returning officers' report, obtained by Fairfax Media, states they "have identified areas of concern which may have bearing on the integrity of the preselection process".

"While it is difficult to raise these issues for the consideration of the State Delegates Council, it is the role of the SDC to consider them as the supreme decision-making body of the Greens NSW in order to make an informed decision about the outcome of the preselection," the report states.