The move puts back the final report, which the commission had previously said it expected to publish by the end of this year, by two months.
A spokesman for the commission said: "The reason for the delay is that we've continued to receive significant submissions, which we've having to consider carefully. Unlike other inquiries we do, this one does not have a statutory time limit, so it's difficult to call time on submissions even if they come quite late in the day."
According to the commission's review timetable, it has spent the past two months considering written responses to the provisional decision it published in September.
This ruled that the CRR regime should remain in place but that some variations might be justified. However, the commission has now admitted: "Although there may be a case for change, exactly how we do it is far from clear cut."
It called for respondents to propose variations and give their views on a proposal to widen the definition of ITV1 to include any ITV+1 or ITV1 HD channel that ITV decides to launch.
ITV's outgoing chairman Michael Grade, who is officially handing over to Archie Norman on 1 January, has agreed to make himself available if the commission holds any hearings on CRR ahead of its decision.
Grade announced in April that he would step down as executive chairman but would stay on until the end 2009 to deal with the CRR review and help the company transition while it found his replacement.