The Standards in Public Office Commission is to meet on Friday to debate if it will open a full investigation into the Minister for Transport, Mr Cullen, and the contracts awarded to PR consultant Ms Monica Leech.
The six-member Commission have so far not discussed the matter but are understood to have read the relevant Department files on the contracts.
They have also studied the report produced last week by former leading civil servant Mr Dermot Quigley which no evidence of impropriety on the minister's part.
The commission's decision will be crucial for Mr Cullen's ministerial future since there will be calls for him to step aside if it decides to launch a full inquiry.
Ms Leech, a political supporter of Mr Cullen from his Waterford constituency, has earned €300,000 since the Department of the Environment hired her as a part-time consultant shortly after Mr Cullen was appointed Minister for the Environment in June 2002.