Paul Duffy, 44, of Somerset Street, Silksworth, Sunderland, penned the hand-written note to Judge Christopher Prince at his sentencing hearing for supplying drugs.

In an unusual move, Judge Prince read an extract of the letter, which would normally be kept private, out to Newcastle Crown Court.

It said: "Heroin is poison. It ruins families and destroys people's souls."

The judge did not read out the rest of the letter, but said: "You are right about that, I hope others will take notice of it".

Duffy was arrested during an undercover police operation targeting dealers in Seaham.

Despite police having evidence of his involvement in just one heroin deal in July last year, when he was arrested in November he admitted he had been supplying to regular customers to fund his own habit.

Prosecutor Michael Graham told the court; "He admitted he had been selling heroin for two months to support his own habit.

"He had been selling six to seven £10 bags per day to regular customers."

Judge Prince said Duffy, who has previous convictions for drugs offences, could have faced two-and-a-half years in jail after he admitted being concerned in the supply of Class A drugs.

But the judge said because Duffy himself gave police most of the evidence to use against him, and the fact he has been free of heroin for over eight months, the case was "exceptional".

Judge Prince told him: "You effectively created the case against yourself.

"In my view you are entitled to more than the normal credit allowed to defendants."

Judge Prince sentenced Duffy to 51 weeks imprisonment suspended for two years with supervision, drug rehabilitation and programme requirements, at yesterday's hearing.

Tony Davis, defending, said Duffy, who has tried "every drug but crystal meth" during his 24-year-addiction, sought help to kick his habit even before his arrest last November and is making impressive progress.

Mr Davis added: "Drugs have destroyed his existence over nearly a quarter of a century."