A judge told a Muslim woman accused of witness intimidation that she had to remove her burka before she could enter a plea in court.
The 21-year-old woman, from Hackney, east London, had refused to take off the full veil and reveal her face at Blackfriars Crown Court, the Judicial Office confirmed.
Judge Peter Murphy said there was a risk that a different person could pretend to be the defendant in the dock and argued that the principle of open justice was more important than the woman's religious beliefs.
He also refused a request from the woman's barrister for a female police officer or prison guard to confirm she was the same person as in police arrest pictures.
The Huffington Post website reported that he told the woman: "I can't, as a circuit judge, accept a plea from a person whose identity I am unable to ascertain."
A Judicial Office spokeswoman said: "There was an issue with the judge asking to confirm the identity of the woman and he has adjourned the case until September 12, when he may hear legal argument about the issue."
The defendant is alleged to have intimidated a witness in Finsbury Park, north London, in June.
Official guidelines were issued to judges in 2009 suggesting a "range of different possible approaches" to the matter of women wearing a burka or niqab in court, but stating that "the interests of justice remain paramount".
The guidelines state: "For a witness or defendant a sensitive request to remove a veil, with no sense of obligation or pressure, may be appropriate, but careful thought must be given to such a request.
"The very fact of appearing in a court or tribunal will be quite traumatic for many, and additional pressure may well have an adverse impact on the quality of evidence given."