Police and customs seizures are driving up the price of P because criminals now face a greater risk of getting caught, says a drug expert.

An annual drug survey made public today shows the price of a gram of methamphetamine, or P, rose from $610 in 2006 to $738 last year.

The Illicit Drug Monitoring System report found the price - commonly regarded as the best measure of police success against the drug - had increased each year.

Lead researcher Dr Chris Wilkins, of Massey University, said large seizures of P and its main ingredient, pseudoephedrine, in the past few years seemed to have pushed up the price.

The drug's availability had recovered slightly at the end of last year, suggesting crime syndicates were re-establishing their supply lines.

But the illegal trade had been badly affected by big interceptions such as a 96kg bust in 2006 and a huge increase in pseudoephedrine seizures from 830,000 tablets in 2003 to more than 5 million last year.

"The people that are making it and smuggling it are seeing large amounts being seized and people they know going to prison, so they demand a higher premium."

Dr Wilkins said he suspected the potency of the drug was also dropping, although researchers did not have enough evidence to be sure.

Drug dealers usually responded to a shortage by diluting the drug before they increased the price.

The survey also found Ecstasy had become far less potent because of worldwide restrictions on the main ingredients of the drug.

Dr Wilkins said dealers around the world had reacted by filling the pills with other substances, including methamphetamine, which could create a highly dangerous cocktail of drugs.

In New Zealand some suppliers appeared to be getting rid of their stocks of BZP (party pills), which were made illegal in 2008, by selling them as fake Ecstasy.

Other trends identified were:

* An increase in the use of new drugs ketamine (also used as a horse tranquilliser) and oxycodone (nicknamed hillbilly heroin in the United States).

* A revival in LSD use, possibly as Ecstasy users look for a stronger drug.

* More methamphetamine users injecting the drug - 36 per cent compared with 23 per cent in 2008 - raising concern over growing addiction rates and health problems.

Dr Wilkins said the survey was too early to pick up drug users' reactions to the Government's methamphetamine action plan last October, which included more money to treat addicts.

Acting national crime services manager Detective Inspector Paul Berry said the price increase of P was good news. Police hoped to see purity and availability levels drop soon.

Researchers interviewed 315 frequent illegal drug users (105 using methamphetamine, 111 using Ecstasy and 99 injecting drugs) in Auckland, Wellington and Christchurch between August and December last year.

BIG NUMBERS

* $610 cost of gram of meth in 2006
* $738 cost of gram of meth last year
* 67 per cent of frequent drug users say they can get meth in one hour or less
* $20 cost of 1.5g of cannabis - unchanged for four years

Source: 2009 Illicit Drug Monitoring System report