Matlick, a 25-year veteran at the tabloid, claims she was fired to make way for an Australian journalist who was already on the paper's staff.
She was dismissed from her job more than a year ago in February 2002 and she claims the Post regularly replaces Americans with Australian and British journalists. In addition, she is claiming that the paper offers little in the way of redundancy pay to women who are sacked by the paper.
Matlick has already filed a complaint with the Equal Employment Opportunity Commission. She claims she was replaced by Australian journalist Geoff Stead. However, the Post has since appointed an American woman, Lauren Ramsby, to the job.
In May last year, News Corp chairman Rupert Murdoch appointed his son Lachlan as publisher of the paper. The 30-year-old Lachlan is already co-chairman of the paper with his father, as well as recently being named deputy chief operating officer of the News Corporation.
He succeeded Brit Ken Chandler, a 29-year veteran of the New York tabloid, who had been publisher of the paper since 1999. Chandler, 54, was a former editor-in-chief of the Post.
In April 2001, the Post's editor-in-chief Xana Antunes was replaced by Australian Col Allan, a former editor-in-chief of the Sydney Daily Telegraph and Sunday Telegraph, who worked closely with Lachlan.
Prior to that, another Australian, Geoff Booth, was made the Post's general manager. He had previously been financial controller of a News Corp newspaper operation.
Former Sun editor David Yelland is another former New York Post journalist, having enjoyed a spell working as deputy editor.
Matlick claims that Lachlan was open about replacing Americans and, according to her statement, he once said: "We really dropped the ball for a while, because we weren't leveraging our skill sets in the UK and Australia".
She argues that the newspaper's management was removed and by the time she was axed, there "a disproportionate number of Australian and UK nationals".
The Manhattan-filed lawsuit is looking for $2m in damages and Matlick's reinstatement as Sunday editor of the New York Post.
In a statement, the Post said, "Ms Matlick's claims of discrimination are simply untrue." It went on to say she was replaced with an American woman and that "the Post does not tolerate discrimination of any kind".
The Post has a daily circulation of around 560,000 and is New York's best-selling daily tabloid, beating its rival the Daily News by some way.
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