Plans for a skirt-only policy for girls at a Deeside high school have been called "antiquated and sexist".
Alyn and Deeside AM Carl Sargeant has backed parents upset at proposals to enforce the policy at Connah's Quay High School.
In a consultation letter, the head teacher said there were "ongoing issues" over girls' uniforms.
Flintshire council said school uniform was "a matter for individual schools and governing bodies."
In the letter, head teacher Ann Peers said girls were wearing "denims, leggings and skin tight trousers".
Mr Sargeant said the proposal "should be dropped straight away" as female students "should have the right to choose whether to wear a skirt or trousers".
He said he understood uniform helped to create "a sense of inclusion and equality", and instead suggested enforcing a policy of wearing "tailored trousers or skirts".
Mr Sargeant added: "If uniform is an issue then of course that should be dealt with and the headteacher would have my full support in that."
He has written to Ms Peers asking her to take parents' and pupils' views into consideration.
Ian Budd, chief officer of education and youth at Flintshire council, said: "School uniform arrangements are a matter for individual schools and governing bodies.
"However, I would urge parents and carers to give their opinions to the school during the consultation period which has been extended to 10 March.
"The governing body will then consider the views expressed during the consultation in conjunction with Welsh Government guidance on school uniform policy, which makes it clear that governors must consider the implications of uniform policy in terms of equalities and affordability, before making an informed decision."
The BBC has contacted Connah's Quay High School for comment.