Susan Gale says her 22-year-old son, Oliver Perver-Gale, is refusing to speak to her after a call she made to police led to his conviction on drug possession charges and an 18-month jail term.

Ms Gale told the UK's Daily Express newspaper she was in turmoil but believed the decision to dob in her son was the right thing to do.

"If by speaking out I can help others avoid the misery I've been through then it will be worth it," she told the Daily Express.

The 57-year-old said she contacted police after finding a packet of brown powder on her kitchen table last April.

A call to a drug helpline indentified the powder as a "class A", or dangerous, drug.

She called police to their Lindfield, West Sussex home and a search of Perver-Gale's car uncovered $19,600 of ecstasy in the boot.

The 22-year-old, who had attended a $50,000 a year private school, pleaded guilty to possessing with intent to supply and is now serving an 18 month prison sentence.

Ms Gale said her son refused to see her, speak to her or answer any of the letters she sent him in prison.

"I have suffered so much," she said.

"Oliver won't speak to me, my ex-partner won't speak to me.

"I just want other parents to know how important it is for us to do the right thing.

"Drugs are evil and destroy people and I don't want that to happen to my son.

"I'm hoping that the experience of going to prison will be the turning point in his life. That's the whole reason I did it."