GARDAÍ routinely value drugs at up to four times the worth given by other police forces, which overstates their success rate and the profits available to traffickers.

An international survey of drug street prices across the English-speaking world shows that Irish police rank values far higher than their international colleagues.

According to gardaí, the price of a kilogram of heroin is €205,000, significantly more expensive than the UK, the US and Australia.

In Los Angeles, where heroin is brought across the border from Mexico – often via Colombia – the average cost of a kilo is €13,250.

Even in the UK, which should have broadly similar prices to Ireland, the kilogram cost of heroin is just €48,500, according to the latest figures.

The revelations come as a comprehensive garda review of all drug street prices is underway, with many of them expected to be further increased in value.

Garda headquarters has only recently reclassified the price of cannabis herb from €2 to €12 per gram as part of its efforts to better reflect street prices.

It leaves the per-kilogram cost of cannabis herb in Ireland way out of line with other international examples at €12,000.

By comparison, a kilo of cannabis herb in the UK would be just €3,450, while in New York and Los Angeles it could be obtained for little more than €1,000.

The statistics do not only bolster crime figures, but also have a potentially much more damaging effect.

Drug dealers can be attracted into the industry, lured by the exaggeration of profits available, and low-level dealers can end up facing far stiffer jail sentences than they would otherwise.

When asked about the review of drug prices, the garda press office said: "The sale of illegal drugs is unregulated and the establishment of the current cost is determined based on the gardaí's knowledge of the market.

"The quality and quantity of drugs available also influences the cost. A review is currently underway into the value/costs of illicit drugs."

Pressed further about the new values for all categories of drugs, it said: "For operational reasons, we are not in a position to provide a list of drug values."

In some countries, police forces do not even publish street prices, believing they are inaccurate and only serve to make drug-trafficking appear more attractive.

A statement from the Singapore Central Narcotics Bureau said it never publicly released drug prices, when making seizures.

Michael Landers of the Drug Enforcement Administration (DEA) in the United States said: "The value of drugs is extremely difficult to determine and will literally change by the day. The quality of the drug can vary enormously and that has an impact.

"We have seen from our work that major seizures can influence prices and in the aftermath of a large operation, drug prices will increase.

"There are variations across different cities depending on how close they are to the borders with Mexico and Canada. There are so many variables, so giving a definitive price is very difficult."

The DEA said it keeps street values under review on a weekly and daily basis to try and judge its own success.

Ireland's cocaine prices are also the second highest in the English-speaking countries looked at as part of the survey.

The price per kilogram of what has become the country's most fashionable drug is estimated by gardaí at €72,000, lower than the drug's value of €86,750 per kilo in the Australian state of New South Wales.

The cocaine price is still significantly higher than in the UK, where a kilogram of the drug would be available for €49,000.

Only when it comes to ecstasy are Irish street prices lower than the other countries surveyed.

With the price of MDMA tablets falling to just €5, that means ecstasy is far cheaper here than in New York, Los Angeles or in Australia.