Ms Spicer, 39, was advised by email last Friday that – after 14 years as a national newsreader with Ten – her contract would not be renewed on December 31.
Ms Spicer today served Ten with a 10-page letter of demand, alleging breaches of the federal Sex Discrimination Act and the Trade Practices Act.
A Ten source said the letter, from law firm Hillman Laxon Tobias, was faxed to the broadcaster's newsroom late this afternoon.
The news reader returned to work last month after the birth of her second child, Grace, in July. She had previously been on maternity leave after having her son Taj in December 2004.
Network Ten had apparently requested Ms Spicer return early from maternity leave to read the new, hour-long 11am national bulletin.
Ms Spicer has been reading this bulletin on Mondays and Tuesdays, in addition to anchoring national evening bulletins on weekends.
Ms Spicer, who has a communications degree from the Queensland University of Technology, was not immediately available for comment.
However, her agent John Fordham said: "We were extremely disappointed and surprised at Ten's decision not to offer Tracey Spicer an ongoing contract, in view of the highly respected standing she enjoys as a newsreader and journalist.
"Since Tracey entered into a management contract with us in August 2005, we have not received a single complaint from Ten regarding her performance, both on air and otherwise," Mr Fordham said.
Colleagues are said to be shocked Spicer will not be on Ten's news frontline next year.
Network Ten said tonight Spicer's contract had not been renewed and thanked her for her years of service.
"Tracey departs with our best wishes and thanks," said Ten's head of news Jim Carroll.
"We hope her career goes well in future."
Mr Carroll added that the network would not be replacing Spicer and that her news reading duties would be taken up by existing Ten presenters.
Network Ten later said the network had not sacked Ms Spicer via email and that they had had ``a number of conversations over several weeks with her manager''.
"It was Tracey's choice that we deal through her manager,'' a network spokeswoman said.
"They requested that we email the letter as an attachment confirming our decision not to renew her contract.''