Amadi, who is director of fundraising at the RNIB, helped to set up the network two years ago, but is frustrated at the rate of progress.
He said: "We have hit a bit of a dead end. In order to have a real impact, we need an injection of resources, such as a dedicated post for someone whose sole responsibility would be to take our work forward."
The network is seeking sponsorship, but Amadi is disappointed at the lack of offers. "Many organisations in the sector say they take diversity seriously, but how many have actually got targets or carry out workforce assessments?" he said.
"They need to stop paying lip service to the issue and put their hands in their pockets. Diversity is important to the cultures and values of the sector, but we still seem to be struggling to get our heads around it. It's time to deliver results."
Amadi said it was important to get more people from ethnic minority backgrounds into senior positions so that there were more diverse role models in the voluntary sector.
"I accept it's not going to happen overnight," he said. "When I go to voluntary sector gatherings I always hope to see more non-white faces, but I so rarely do."