Urgent: What are the laws on tying my dog up?

I have a six month old puppy, im trying to house train her but she still does it in my house, i have now started to tie her up outside in my back yard but not all day just for a few hours and i put a bowl of water out for her, i can't just leave her untied in my garden as i live on a corner and my garden is not secure despite attempts of asking the council for new fencing replacing the hedge, they said no it has to come out of mine and my husbands money but with 3 kids and 4 animals, i can't afford it, not on benefits, so what else am i to do and i don't tie her up and then go out, i'm always in and if i do go out i leave her in my kitchen so it is easier to clean up. Please someone help me, i need advice on what to do and i feel like i'm being cruel to her but i don't know what else to do, when i take her on walks when i have time which is once a day normally, she won't do anything except play up and jump around. I love my animals and my big dog who is 11 years old i can let him in my garden with supervision, he does his business then comes in, why won't she learn from him, instead she runs into my front garden then gets through the hedge despite telling her no and tapping her nose, but now i have given up tapping her nose because she simply is not learning her lesson. I only hope i am not breaking any laws. This matter is rather urgent and i would appreciate it if anyone could help me ASAP.