Timu points to the Waka Moemoea Trust, of which he is a member, established with the idea that "gangs are the best people to get gangs off P".
The charitable trust offers health, education, employment and housing services to help "hard-to-reach families".
"Unfortunately, any funding to the trust has had to be kept low key because the idea of the trust receiving public money to address the issue of P within gangs was not politically palatable," Timu wrote in his submissions.
Public records show Waka Moemoea received $812,000 in government grants or contracts in 2014/2015 financial year, and posted a $129,000 deficit.
Timu pointed to comments posted on blogs as evidence the Mob was "prejudiced by institutional and interpersonal racism on a daily basis".
"They are viewed as 'thugs on drugs', criminals etc and have found it extremely difficult to access services for those members affected by P, including their children and mokopuna," Timu wrote.
"They are turned away because of who they are and how they look, yet just like all other people, they too have dreams, ambitions and hopes for themselves including their wives, children and mokopuna but the racism and bigotry they encounter every day prevents them from living full, rich and healthy lives."
Timu said the Crown had a duty to address the methamphetamine epidemic among Maori, including the Mongrel Mob.
"If the Crown cannot adequately address the P epidemic, then the Crown must ensure that there are adequate services available to help those affected by P that do not turn people such as the Mob away, simply because of who they are."
The claim asks the Waitangi Tribunal for a number of recommendations, including a finding that the New Zealand health system is "inherently racist" and seeks a review of the policy decision-making process.
Read the full Waitangi Tribunal claim