"We have had a couple of reports that seem to favour the option of leaving it there but there's a whole lot of reports referenced that we haven't seen.
"This is the concern. They come out sounding very credible about how this is the best option but there's not the information to support that," he said.
Community consultation meetings set up for next week by the Swedish Club were described by Mr Makgill as "a controlled release of information as a public relations exercise".
Environmental marine scientist Dr Shaw Mead said the information they had already received appeared to be lacking in the most important aspects, including the alternative wreck options and environmental effects.
Cultural adviser Buddy Mikaere said there had not been much engagement with local kaumatua on Motiti Island, or on the mainland.
Mr Mikaere said the group was strongly opposed to leaving the Rena on the reef.
The Swedish Club spokesman Hugo Shanahan said iwi groups already had available draft assessment reports from which they planned to get feedback from the wider community.