According to Deadline, the actresses will be joined by Rupert Friend on the series which is based on the bestselling novel of the same name by Sarah Vaughan.
The 2017 book focuses on high-profile Westminster politician James Whitehouse (Rupert) whose marriage begins to unravel when he is accused of rape.
Show: Sienna Miller and Michelle Dockery are leading the cast of the new Netflix series Anatomy of a Scandal (Sienna pictured in November 2019)
His wife Sophie (Sienna) is convinced that he is innocent and will do whatever it takes to protect her family in the wake of the scandal.
Meanwhile, criminal barrister Kate (Michelle) is equally convinced that James is guilty and is determined to see he pays for his crimes.
The show is from Big Little Lies creator David E. Kelley and former House of Cards showrunner Melissa James Gibson.
S.J. Clarkson of Succession and Jessica Jones is reportedly slated to direct the six-part series.
New role: According to Deadline, the series is based on the bestselling novel of the same name by Sarah Vaughan (Michelle Dockery pictured in October 2019)
An idea is said to have been put forth that the show could become an anthology, with future seasons focusing on different scandals.
Anatomy of a Scandal was ordered to series at Netflix in May and will be shot in the UK at a later date.
Further details about the rest of the cast or when the series will be released are yet to be confirmed.
Michelle was most recently seen in the AppleTV+ series Defending Jacob alongside Chris Evans, where she played a mother dealing with an accusation that her 14-year-old son is a murderer.
Sienna starred in drama film Wander Darkly this year while she also appeared as Roger Ailes’ wife Beth in the miniseries The Loudest Voice released last year.
Story: His wife Sophie (Sienna) is convinced that he is innocent and will do whatever it takes to protect her family in the wake of the scandal while barrister Kate (Michelle) thinks he’s guilty