Singer Melissa Etheridge has shot an advertisement asking voters in Colorado to support a new bill to legalise marijuana.

The Come to My Window star began using medical marijuana a few years ago to reduce the side effects of chemotherapy after being diagnosed with breast cancer in 2004.

Now Etheridge is urging fans to help pass the Amendment 64, which would make the use of pot legal in the state for persons above the age of 21 years. The drug would also be taxed in a similar manner to alcohol.

In the clip, uploaded on, the 51 year old says, "A few years ago I was going through cancer chemotherapy and I was suffering... It was terrible. Prescription drugs were not helping. The only thing that allowed me to function and regain my strength was marijuana and I'm grateful for the relief it provided me.

"You know before I needed to use marijuana I just accepted the laws that treated marijuana users as criminals. But it's funny how a serious illness can give you a new outlook on life."

She adds, "I now see that it's wrong to arrest adults for using marijuana and it's even more wrong to allow gangs and cartels to profit from selling marijuana.

"Instead we should allow adults to possess limited amounts of marijuana and we should regulate marijuana sales in order to generate tax revenues for public schools construction and other community needs. To me, regulating marijuana is simply the right thing to do."