The Royal Commission of Inquiry into the Pike River Coal mine disaster, which claimed the lives of 29 men, will need more than 15 weeks to examine key issues, a families' spokesman says.
The inquiry into explosions at the West Coast mine last November will open with a preliminary hearing in Greymouth on April 5.
The commission said it intended to hold 15 weeks of hearings, beginning on May 6 and finishing on November 4.
But Bernie Monk said the timeframe was inadequate and he was worried shortcuts might be taken.
"None of this short-cutting and making it short just for the sake of the length of the inquiry, no, we're not happy with that," he told Radio New Zealand.
"It's got to start with how Pike River was actually initially started and where it went from there, right back to the day when the first survey pegs were put in."
Nicholas Davidson QC, who represents some of the dead men's families, told NZPA he did not want to comment on the inquiry setup.
"We've only just received this and the commission clearly has given a lot of thought to how it is going to proceed and there's a logic in what they are proposing to do.
"We will have to digest that and fit our own representations and submissions to them within these timeframes as everyone will..."
However, he would make submissions at the preliminary hearing about "some matters of particular concern" to the families.
He could not go into detail about those concerns.
"We essentially intend to say what we wish to say within the commission not by way of media statement. It's not appropriate for us to run a parallel case outside the commission...
"From our own inquiries there is a great deal of material that we wish to put before the commission."
The hearings will be organised into four phases, the first of which would examine New Zealand's regulatory environment and the geography, approval and development of the mine.
The second phase would explore the search and rescue operation, and the cause of the deaths, the third phase the cause of the explosions and Pike River Coal's practices, while the last would focus on policies governing mining.
The inquiry would seek to establish what happened at the mine and to identify how to prevent mining tragedies.