Image copyright AP Image caption Judge Aaron Persky has been heavily criticised for sentencing Brock Turner to only six months in jail

A US judge who faced criticism over his sentencing of a Stanford University student convicted of sexual assault has been removed from a similar case.

A prosecutor filed a challenge against Aaron Persky, a Superior Court Judge in Santa Clara, California, alleging bias.

The case from which he was removed involved a male nurse accused of sexually assaulting a sedated patient.

Mr Persky came under fire last week when he gave the student a sentence that many regarded as too lenient.

Image copyright AP Image caption Brock Turner was seen by two witnesses sexually assaulting an unconscious woman

In the latest case, Santa Clara County District Attorney Jeff Rosen filed the challenge arguing that the judge was biased.

The request came a day after Judge Persky dismissed a misdemeanour stolen mail case in mid-trial.

"We are disappointed and puzzled at Judge Persky's unusual decision to unilaterally dismiss a case before the jury could deliberate," Mr Rosen said in a statement.

"After this and the recent turn of events, we lack confidence that Judge Persky can fairly participate in this upcoming hearing in which a male nurse sexually assaulted an anesthetised female patient."

Mr Persky first stirred controversy after handing down a six-month jail sentence to former Stanford student Brock Turner, who was seen by two other students sexually assaulting his unconscious victim behind a rubbish bin.

The victim's statement read in court went viral, prompting public outcry over the sentencing.

Three petitions have circulated calling for the judge's dismissal, including one that included more than a million signatures.