Have they communicated as such in writing, as any rejection of leave must be stated in writing by employer with such valid reasons ?
Have you specifically stated the reason for such leave as "Child Care" in your application ?
If so, contact the Union or Legal Services Authority, and also make a separate representation to the Higher Authority as grievance in their on line portal pgportal as human rights angle is also involved. When even convicts can take such Parole, why not alleged ? Have you stated in application that you can come as and when you are called for investigation on your own costs on such dates as decided by competent authority ?
Send it by Regd post, and specifically record such refusal. A copy may also be sent to higher authorities. To sanction or rejection with reasons is the law. But rejection of leave application was unheard and amounts to failing in duty.