A major report on fracking in New Zealand has been set back again, due to the complexity of the investigation.
Parliamentary Commissioner for the Environment Jan Wright said her office required more specialist advice to complete the investigation, and she was unlikely to meet her deadline of mid-2013.
She had originally planned to release her report into the controversial practice of hydraulic fracturing in New Zealand at the end of last year.
Instead she released an interim report in November, and said a full review would be released in the middle of this year.
Dr Wright told a select committee this morning: "We're at such an early stage and we don't really know what we are going to uncover."
She noted that her office was small, and her staff had put on hold other important projects in order to finish the fracking report.
"I'm going to be asking for a bit more money ... I've actually had a decrease from when I first started.
"We have to buy in some specialist advice on some of these issues because these environmental issues are very complex."
Dr Wright also clarified this morning that her interim report was not a "ringing endorsement" of fracking.
It said the risks of the unconventional mining practice could be managed if best practice was followed.
Her report found that government oversight and regulation is complex and fragmented, and that regulation may be too light-handed.
It also found that energy companies had not earned public trust.
Fracking helps release natural gas and oil deposits by pumping large volumes of mainly water and sand at high pressure into deeply buried, gas-bearing rock.
The practice has been used in the Taranaki region, on a small scale, for two decades.