The father of two Danville children killed when a drunk driver high on pain killers ran them down has begun pushing for a ballot measure to tax prescription drugs to fund the state's drug-tracking system.

California's secretary of state cleared 56-year-old Robert Pack of Danville on Tuesday to seek signatures to put his proposal before voters.

The Oakland Tribune reported Wednesday the measure would impose a quarter-cent-per-pill tax.

The money would fund the state's Controlled Substance Utilization Review and Evaluation System, a database that tracksthe dispensing of prescription drugs like pain killers to detect possible abuse. The system was threatened by state Justice Department budget cuts.

Pack's 7-year-old daughter and 10-year-old son were killed in 2003. Jimena Barreto was serving 30 years to life in prison for second-degree murder.