Holt, 28, joined the Strictly team in 2008 and partnered swimmer Mark Foster on the sixth series. She had previously appeared on New Zealand's Dancing With The Stars.
"I'm not too sure why I wasn't asked back. They didn't really give me a reason," she told The Mirror.
"My agent had to ring them up to find out what was going on. It leaves me wondering why. It is frustrating."
Fellow professional dancer Karen Hardy confirmed yesterday that she will have a reduced role in the upcoming seventh series.
Katya Virshilas, 25, and Natalie Lowe, 28, are expected to replace the pair.
A BBC spokesperson commented: "We contract dancers for one series at a time and the lineup is always subject to change. We thank Hayley for her fantastic contribution to the show. It is an amicable decision."