4 day week

I want to reduce my working week from 35hrs possibly by 1 day to 28hrs. my employeer said no, then said ok , but it will have to be down to 20hrs or stay at 35hrs. Can they do this to me. I work in the public sector.

Why can they not do it? You are the one looking for a change in hours they have made you in effect two offers 35hrs or 20hrs its up to you to decide