Mark Astarita, director of fundraising at the British Red Cross, has also been appointed to the Institute of Fundraising's trustees board.
The appointments have been made to build the Institute's membership strategy and policy development, and bolster the DMA's relationship with marketers in the charity sector.
Barnes and Astarita join 15 other board trustee members at the Institute of Fundraising, including: Alan Gosschalk, fundraising director at Shelter; Sarah Lyness, executive co-director of fundraising and marketing at Cancer Research UK; and Joe Saxton, head of fundraising at The Scout Association and the Institute's current trustee board chair.
Barnes said: "Best practice and sector growth lie at the heart of both the DMA and Institute ethos and it therefore makes sense that we are increasingly working together to tackle the common issues facing our industry.
"As a trustee of the Institute, I hope to be able to further that relationship and contribute to the growth and success of this outstanding professional body."