Sally Clark is using an ancient law to sue the pathologist who carried out post-mortems on her sons for damages.
Sally Clark was freed in January 2003
Her representatives said she had made the high court claim because she was out of pocket as she had not been fully reimbursed for her legal costs.
The case against Dr Alan Williams is being brought under the 17th century misfeasance in public office law.
Mrs Clark spent three years in jail for the murder of her two baby sons before being cleared two years ago.
Dr Williams was found guilty of professional misconduct at a General Medical Council hearing in June over evidence not disclosed to Mrs Clark's 1999 murder trial.
Mrs Clark's legal costs amounted to £270,000, but her spokeswoman Sue Stapely, of Quiller Consultants, said she had been "denied" £120,000 because of the complicated process. Dr Williams has never been liable for these costs.
The high court claim under the ancient law was issued last year, but was put on hold pending Dr Williams' disciplinary case.
The hearing earlier this year banned him from doing court work for three years, although he is still allowed to practice as a pathologist.
The GMC heard Dr Williams had not disclosed microbiology results from a post-mortem examination on one of her sons which suggested he may have died from an infection.
The high court claim for damages, which accuses Dr Williams of negligence as well as misfeasance, centres on that post-mortem examination.
In a statement, Sally Clark and her husband, Stephen, said: "It is a private matter and we simply wish to get on with our lives."