Why washing machine leaks from bottom when not in use?

Washing machines are connected to your mains water supply so either there is a problem with your water supply in as much as it is continually leaking when it's not supposed to be in use, or, more likely, there is a blockage in the machine or the water pipes immediately surrounding it which is causing water to flood back out of the machine. It's usually a small item of clothing like a sock (or a collection of them) that has worked its way out of the machine via that gap at the front of the drum just next to the door, and is now blocking your pipes. You may find water bubbling back out of your sinks and bath, depending on their proximity to the washing machine. You need a plumber, quick!