"His sheets are also changed two-three times per week. So his laundry part of food/laundering would be at least $4-$5."
It leaves 17-year-old Eamon with little more than $4 each day for all food at the residential care home he lives at in the Hawke's Bay.
It's substantially less than a prisoner spending the night in police cells is allocated.
Figures released to Marshall from the New Zealand Police under the Official Information Act show a person detained in police custody overnight attracts funding of $10.25 for dinner and breakfast and $3.25 for laundry.
By comparison the New Zealand Defence Force said its budget guide for daily food costs was $20.32 alone for Navy personnel on ships. This figure fluctuated depending on where the ship was deployed.
Marshall said he was dismayed at the low cost allocated to disabled people for food.
"In my view it is a poor reflection on the government that it is prepared to fund food for disability persons at a lower rate than it is prepared to fund a prisoner in a police cell.
"For many of those disabled people a nice meal is one of the few highlights in their day."
A 2018 New Zealand Food Cost survey by the University of Otago put the average cost of healthy food for an adolescent boy at $74 per week.
Eamon gets $63.80 for food and laundry, making his diet "extremely limited".
Marshall said he and his wife Fran, who visit their youngest child most nights, regularly take him low-sugar home baking.
The couple made the heartbreaking decision to give up care of Eamon when he was 18 months old because of his high and complex needs.
They have fought for his rights and the rights of the disabled community since.
"This is a human rights issue. They're just getting left behind.
"It's not just about nutrition but it's about taste. For such a small amount of extra money you could provide such a profound difference to their life."
In a response to Marshall's questions about funding for Eamon's food, the ministry's head of disability Adri Isbister, said laundry and food costs were minimal in the context of overall residential funding and were shared across the number of people in the home.
When asked by Marshall why the ministry did not separate out food and laundering costs, she said Disability Support Services did not fund providers at "this detailed level of assessed need".
When asked if the ministry would be happy for one of their family members to be funded $4 per day for food, Isbister said the provider was responsible for delivering appropriate and quality service within the overall funding envelope.
The Herald has sought comment from the Ministry of Health.
In November the New Zealand Disability Support Network (NZDSN) briefing – Enabling Good Lives Sooner Rather Than Later - reported there was a $574 million gap in disability funding.
The paper said providers were struggling to keep afloat in an environment that doesn't allocate enough money to meet clients' needs.