the tap washer may be stuck and need replacing. the tap body may need replacing as is broken. the best way to find out is by turning the main stop cock off and turn the hot and cold taps on at wash hand basin until water stops. take plastic cover plate at top of tap off. take screw out that holds tap head to tap body. get spanner and unscrew tap body. go to plumbing supplier and get new body. replace and turn water back on. check for leaks.
alan [plumber], June 2009