Someone posting from Attawapiskat Chief Theresa Spence's Twitter account called Sen. Patrick Brazeau a "typical colonized Indian a--hole" on Thursday.
Brazeau, a Conservative senator and aboriginal, has been critical of Spence and fiscal management on reserves.
The tweet has since been deleted, but not before other Twitter users took notice.
Spence spokeswoman Lowa Beebe said on Twitter the post wasn't from the chief. She said Spence's supporters set up the account, @ChiefTheresa, and three people have access to it.
In response to the insult, Brazeau tweeted: "Regarding Ms. Spence's comment towards me, contrary to much advice, I will not "dis-Spence."
He later told QMI Agency, via Twitter: "I'm not concerned with personal attacks. My focus is 2 advocate for greater accountability b/c FN ppl deserve it from their leaders."
Thursday marked the end of Spence's 44-day fast during which she subsisted on fish broth and tea to protest the federal government's treatment of aboriginals.