Covert police tactics developed in Vancouver to extract confessions has come under fire in Australia after cops there lost their bid to protect the secrecy of the undercover methods.

Some of Australia's top cops now say that the public disclosure of the undercover strategies could put lives at risk and jeopardise future operations.

A Victoria Police spokesman said some investigations in Australia had already been stopped for fear they could be compromised by publicity about undercover methods.

The investigation techniques pioneered by RCMP officers in Vancouver are designed to lure confessions out of criminals.

It involves police officers pretending to be hard-core criminals and is played out in what is called "Mr. Big" undercover scenarios.

One of the most significant successes of the "Mr Big" technique resulted in confessions from Sebastian Burns and Atif Rafay, who were charged with the triple-murders involving members of Rafay's family.

The two were found guilty last summer of killing Tariq Rafay, his wife Sultana and their 20-year-old autistic daughter, Basma. The victims were found beaten to death with baseball bats in their suburban Seattle home in July, 1994. They were killed for insurance money.

The men, both 28, will spend the rest of their lives in a U.S. prison with no chance of parole.

Burns and Rafay fled to their native West Vancouver after the killings which triggered a RCMP sting investigation.

Police officers (whose identities have been protected by the court) posed as shadowy gangsters who at first pretended they wanted to invest in a film the young men dreamed of making.

Later, the officers told the suspects they were well-connected criminals and wanted the young men to join their network. But first they had to come clean with their respective pasts and admit to any crimes.

In a series of secretly videotaped encounters at hotel rooms from Whistler to Victoria, the young men admitted to killing the Rafay family. Canada eventually agreed to deport the pair to the United States but only after securing a guarantee that the young men would not face the death penalty.

The RCMP has a perfect record in convicting suspects who have fallen into this trap.

The techniques made headlines in Australia recently after The Age newspaper successfully sought the lifting of a court ban on reporting on the undercover methods.

But the paper chose not to reveal details of the police tactics to avoid compromising sensitive investigations.

Victoria Police spokesman Stephen Linnell said the force was "clearly disappointed" by the appeal outcome.

"These investigations have been highly successful, and they're not the sort of thing we wanted discussed widely in public," Linnell said.

There have been at least three recent murder convictions in Victoria based on confessions obtained by undercover police using the method to win the confidence of offenders.

Australian critics of the controversial tactics claim they are unfair because they involve suspects being questioned without being warned of their rights.

Victorian Law Institute president Chris Dale said the covert techniques strike at the very heart of the judicial system." It completely short-circuits the safeguards that operate within our system to protect people charged with crimes," he was quoted as saying.

Australian Police Association secretary Paul Mullet said the "crime boss" technique to solve crimes is a vital policing tactic.