Bernie Monk, whose son Michael died in the mine, said it was outrageous to still be waiting for a prosecution.
"They owe this to the country to do the right thing and I can't understand why we're still here, still battling for the same thing."
To honour the anniversary, Monk said families would meet at the memorial site in Atarau on Wednesday morning, before heading up to the mine in the afternoon.
"We'll all gather at approximately the time of the explosion and have a roll call, so every member is remembered by individuals. If their families are not there, we still have their names recorded and then we have a minute silence.
"That's a vigil that we've had every year since the day it's happened and we'll continue to do that, until the government, the police and the Crown see sense in bringing charges and possibly getting the men out."
The 15th anniversary also comes after the release of the Pike River feature film, which has brought the families' ongoing fight for justice back into focus.
Recently released research shows New Zealand's health-and-safety record remains poor, with workers here more likely to die than in Australia or the United Kingdom.
The Public Health Communication Centre research identified persistent issues with workplace health and safety, including weak enforcement, inadequate fines, and poor understanding of legal duties among employers and political leaders.
Anna Osborne, whose husband Milton died in the mine, and Sonya Rockhouse, whose son Ben was also killed in the disaster, are in Wellington to meet with Workplace Safety and Relations Minister Brooke van Velden.
Osborne said she was shocked, but not surprised there had been little change in the rate of workplace fatalities in the last 15 years, and she wanted to see health-and-safety regulations strengthened.
"We lobbied the government for stronger health-and-safety rules and regulations in the workplace, but to find that they're being watered down at the moment by the government, it just makes me sick to think that another Pike River could actually happen again."
Osborne said people dying at work and not returning home to their families was unacceptable.
"I've lived through losing my husband and it's a nightmare. It's an emotional rollercoaster and life just is not the same.
"I just hate the thought of any loved one not returning home after their day at work, so if I can help in any way to push these laws to make them stronger and make it safer, I'm going to do that."
Osborne said she felt she owed it to the people of New Zealand, who had been so kind in supporting the Pike families, to keep fighting for safer health-and-safety regulations in the workplace.
A police spokesperson said they were still working with the crown solicitor and considering whether to lay charges over the Pike River Mine disaster.
They could not provide a timeframe for when a decision would be made on the matter.
