I think it best to find out what is causing the earth leakage first,not knowing what voltage your supply is or what country you are in, continue to measure (with a friends help) the leakage voltage whilst you go around switching each individual item on the circuits off and hopefully you will come across the culprit, or culprits that are causing this, then you can investigate ways of improving the leakage by testing that individual piece of kit or simply remove / replace it.
Charlie, February 2009