The tragedy of a Perth mother who was punched to death and left in her home with her children undiscovered for weeks has spurred a push for a 20-year penalty for lethal domestic violence in Western Australia.

Saori's Law, as the opposition's amendment bill was named on Monday, seeks to double the penalty for so-called one-punch deaths in cases of domestic violence from 10 years to 20.

The law refers to the December 2010 case of Saori Jones, 31, a Japanese-Australian woman punched by her partner, Bradley Wayne Jones, 34, in front of their two toddlers and left to decompose in their suburban Perth bedroom, where her body remained for two weeks before it was found by police.

Jones was jailed last year for a minimum three years, after pleading guilty to manslaughter, and will be eligible for parole in December 2013.

Opposition Leader Mark McGowan said he would introduce the bill on Wednesday.