My work has just imformed me that I am no longer allowed to wear trousers (including all female employees). So we are being forced to wear only skirts EVERYDAY regardless of the weather....
I'm not an employment law expert but I'd imagine they can yes. There are plenty of jobs where a uniform is required. I've never seen an air stewardess wear trousers for instance. I guess there might be limits in the way they can introduce it but I expect they can do so.
As far as I know they can not force you to wear a skirt as this is discrimination against you as a female. I had this problem several years ago when I worked for Tescos and was told that I was not allowed to wear trousers as part of my uniform. I go my union rep involved and they gave in as it was proved to be discrimination. Unless they are going to make the men wear skirts too!