The long-promised NSW Drug Summit begins on Friday in the regional city of Griffith, before hearings in Lismore and Sydney.
All but the opening speeches in Griffith had been closed off to media until a late decision to allow in reporters to hear the co-chairs summarise each session.
Lists of the 49 groups attending were also circulated to media on Thursday as the government sought to hose down complaints of some stakeholders being left out, including a Griffith homelessness organisation.
An election promise, the summit aims to build consensus and social licence for major drug reforms - modelled on a week-long forum in 1999 that proved the impetus for Australia's first supervised injecting room.
Advocates want serious consideration of community drug checking, improved funding of addiction services and changes to policing.
But Sam Kidd, the campaign manager of national drug policy reform organisation Unharm, expressed concern the latest developments illustrate a lack of desire to make meaningful change.
"There's been a pretty deliberate attempt to minimise the impact of this summit," he told AAP.
"The Sydney hearings are after the parliamentary year ends, the report is not due until February ... by the time they respond, it might be 18 months out from an election.
"Is that the time they are choosing to enact significant law reform?"
Another source told AAP people inside the sector were "furious" about how the summit had been organised, saying it raised serious questions about the Sydney hearings.
The fact Griffith City Council was not invited did not offend mayor Doug Curran and he accepted everyone could not attend.
But he aired concern local housing support service Linking Communities would not attend.
"Our community has been chosen because, like many towns in regional NSW, there are certain drug problems here," Cr Curran told AAP.
"The (health and housing) ministers are in town and that's good but it's actually the next step that's important.
"We hope it's not just a summit to tick the box of having a summit."
Friday's forum is expected to hear from people across the drug spectrum, including those with lived experience, health workers and police.
"There's been no effort, certainly no concerted effort, to lock anybody out," Premier Chris Minns said on Thursday.
"We do have the experts in the room to provide the best information and also evidence that will challenge government policy.
"(There will be) things that I won't necessarily agree with ... but we want them around the table to challenge the prevailing system."
A spokesman for Health Minister Ryan Park said the summit would capture the many and diverse views of more than 450 invitees, three times the attendance of the 1999 drug summit.
NSW Health advised Linking Communities has been invited.
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