The 53-year-old said she would continue to represent Tasmanians as an independent member of federal parliament.
"It's become clear to me that I no longer have the confidence of the Jacqui Lambie Network to be able to represent it in the Senate," she said on Thursday.
"While Jacqui has not kicked me out of the network, she has suggested that I go it alone."
The defection leaves the party with one member in federal parliament, weakening its power and allowing Senator Tyrrell more autonomy to vote on legislation.
I wanted you to hear it from me. — Tammy Tyrrell (@TammyTyrrell_) pic.twitter.com/zzOebqFEBiMarch 28, 2024
Senator Tyrrell said it was a tough decision but she did not want to damage Senator Lambie or her party.
"With that in mind, the best thing I can do is to step aside to allow the network to shine," she said.
"I don't want to hold them back. I want to see Jacqui and the JLN continue to succeed.
"I believe this is the best thing for Jacqui, the network, myself, but most importantly, the people of Tasmania right now."
Senator Tyrrell was elected to the upper house in 2022.
Prior to entering parliament, she worked for years as Senator Lambie's office manager.
The Jacqui Lambie Network won at least two and possible three seats at the Tasmanian state election, with the party locked in negotiations over support for a Liberal minority government.
Senator Lambie entered federal parliament in 2013 as a member of Clive Palmer's United Australia Party, but left within months.
She later resigned from the Senate after discovering she was a dual citizen, but was re-elected under the Jacqui Lambie Network banner in 2019.
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