Any person who uses towards a girl of or over the age of 12 years and under the age of 16 years any lewd, indecent or libidinous practice or behaviour which, if used towards a girl under the age of 12 years, would have constituted an offence at common law shall, whether the girl consented to such practice or behaviour or not, be liable on conviction on indictment to imprisonment for a term not exceeding F1ten years or on summary conviction to imprisonment for a term not exceeding three months.