A 7-year-old child presents to the paediatric clinic with amiguous genitalia increasing with age. On examination her height, weight and blood pressure were recorded within normal limits. Labia appeared bifid with 2 separate perineal openings, phallic length was 2.5 cm and no palpable gonads were noted in the inguinal region. USG shows presence of mullerian structures. The most probable diagnosis is-