Al-Faisal's remarks, made in the US where he was attending the Middle East conference in Annapolis, were carried by the state Saudi Press Agency.
On Saturday the Saudi justice ministry said the rape victim was a married woman who allegedly confessed to cheating on her husband.
It said she and her lover had met in his car for a tryst "in a dark place where they stayed for a while".
The ministry also condemned foreign interference in the case.
The girl, 19, who was sentenced to six months' jail and flogging, said seven men raped her in Qatif in 2006 after she had gone to retrieve a photograph of herself from a high school friend after just getting married.
She said two men got into the car they were in and drove them to a secluded area where others waited before she and her companion were both raped.
The initial sentence of 90 lashes for being alone with a stranger was increased to 200 on appeal, drawing international media attention.
The US expressed astonishment but not condemnation.
The jail sentences against the seven men convicted of gang raping the girl were increased to between two and nine years.
The initial sentences for the men ranged from 10 months to five years in prison.
Saudi's strict interpretation of sharia or Islamic law, prohibits women from being seen publicly in the company of men other than close male relatives.
Women are also often sentenced to flogging and even death for adultery and other crimes.
The case has sparked rare domestic debate about the kingdom's legal system which gives judges wide discretion in sentencing criminals and where accused sometimes get no legal representation.
Saudi justice is administered by a system of religious courts whose judges are appointed by the king on the recommendation of the Supreme Judicial Council.