"I apologised to a few Maori friends of mine today, stating that my bio in Maori was wrong. They were more understanding and still pledged to vote for me.
"Maori Translate was used and it came out wrong. I also had my bio translated into Chinese, but that translation was totally correct as it was accepted by the Chinese Association of Waikato.
"I have held myself accountable. I have been honest and shown integrity by apologising straight away. Apologies to all my Maori friends - there was no intention to insult. The only intention was to be inclusive and I feel ashamed for getting parts wrong.''
Former Maori Television presenter Te Hamua Shane Nikora is among those upset.
"When your intent isn't genuine, you don't go far enough to get it done properly,'' he wrote on his Facebook page.
"This man lives in a city where the university majors in Te Reo Maori! He could have paid a student from Te Tohu Paetahi to translate his pamphlet. But no, he only wants votes. He don't really give a toss about us or our language.''
Te Tohu Paetahi is a total immersion Maori language and teaching programme offered at the University of Waikato.
Casson's supporters back him - sending him messages of encouragement and applauding his intentions, despite the mistake.
One wrote: "It's all good, mate. Those of us that are of Maori [descent] and know you as a person and what you have done for us in and around the most troubled community know your heart. We are very grateful that you continue to acknowledge our Maori people and altogether diverse communities to the best of your ability.''
Another said: "Keep up the great work, James. I know your heart was in the right place in helping many Maori people here in Waikato - all credit to you in being honest.''