The analysis, which was performed at the Cardiff Metropolitan University, Cardiff School of Sport on July 9, revealed that most of Williamson's deliveries exceeded the 15 degrees level of tolerance permitted under the regulations.
Williamson, who was reported after the Test match against the West Indies in Trinidad last month, can apply for re-assessment after he has modified his bowling action in accordance with clause 2.4 of the Regulations for the Review of Bowlers Reported with Suspected Illegal Bowling Actions.
The off-spinner joins a list of players suspended by the International Cricket Council for an illegal action including India's Harbhajan Singh, James Kirtley of England, Jermaine Lawson and Shane Shillingford of the West Indies and Pakistan's Shoaib Malik and Shabbir Ahmed. Sri Lanka off-spinner Sachithra Senanayake was also recently suspended.