Less than 1 percent of characters on primetime network television have disabilities and their numbers are on the decline, a new report indicates.

Of the 647 characters appearing regularly this year on scripted programs on ABC, CBS, The CW, Fox and NBC, just five have disabilities. That’s down by one from last year.

The findings come from an annual report on minority representation on television released Wednesday by the Gay & Lesbian Alliance Against Defamation. It’s based on an analysis of the 91 scripted shows that networks have announced for the 2011-2012 season.

“People with disabilities represent our country’s largest minority,” said Christine Bruno, co-chair of the Tri-Union I AM PWD campaign to promote inclusion of people with disabilities in entertainment, which helped conduct the report. “We look to our stages and screens not only for entertainment, but to hold a mirror up to society. Our industry has a responsibility to its artists and the viewing public to accurately reflect what we see on our streets and in our communities.”

The characters with disabilities that are represented regularly on television this season include Max Braverman on NBC’s “Parenthood” who has Asperger’s syndrome, a character on Fox’s “Glee” who uses a wheelchair, the lead on Fox’s “House” who uses a cane, a character on CBS’s “CSI: Crime Scene Investigation” who uses prosthetic legs and a woman on Fox’s “Raising Hope” who has Alzheimer’s disease.

Three recurring characters with disabilities are also expected to appear in roles on “Glee” and “Family Guy” on Fox as well as ABC’s “Private Practice.” But that represents just half as many recurring characters with disabilities as last year, the report found.

Cable television fared somewhat better, with at least 10 regular and four recurring characters with disabilities. They included individuals with everything from Down syndrome, cerebral palsy and hearing impairments to cancer.

Notably, the report indicates that in contrast to network television, many of the characters on cable are portrayed by actors with disabilities themselves.

“This is evidence of positive change,” Bruno said. “More cable producers and writers than ever before have demonstrated a commitment to authentic casting and accurate storylines. The success of these programs reflects the evolving attitudes and appetites of viewers, and puts those who create them ahead of the curve, creatively and financially.”