A corrupt pharmaceutical industry is providing Chinese drugs gangs with chemicals allowing them to produce tonnes of methamphetamine, said a United Nations drugs official.

Speaking in the wake of the seizure of 2.4 tonnes of the drug in Lufeng district, Guangdong Province, earlier this year, senior UN drugs official Jeremy Douglas said that "corruption in the pharmaceutical and or chemical industries'' in China was behind the easy availability of chemicals necessary to make the drug, reports the South China Morning Post.

"To operate a lab like this, you need a lot of chemicals, which are legitimate, regulated chemicals from the pharmaceutical industry," Douglas said, after being briefed on the drugs seizure by Chinese officials.

The remarks come after a clampdown on drugs crime in the province: a hub in the production and distribution of methamphetamine, known locally as "ice".

"This group has been able to get their hands on the precursor chemicals necessary to produce the drugs. They've been doing it for a long time, which means they're getting these chemicals on a regular basis," said Douglas.

"There is some kind of corruption in the chemical/pharmaceutical industry taking place allowing this to happen."

In recent months, there have been a number of high-profile seizures of Chinese produced meth.

Launched last year, the "Ban Drugs in Hundreds of Cities" operation has so far led to 60,500 people being arrested, reports state news agency Xinhua.

In November, 3,000 officers were involved in an anti-drugs operation in Guangdong, seizing 2.7 tonnes of the drug, and 20.8 tonnes of chemicals used to make the drug.

The chemicals ephedrine and pseudoephedrine, which are used to make cold and flu remedies, are also used for making methamphetamine.

In a raid in Jakarta, Indonesia, led to the arrest of 11 members of a China-controlled meth gang, and seized 8.1kg of the drug.

China has an estimated 6.5 million methamphetamine addicts, according to official figures.

The drugs and their raw ingredients produced in the country are shipped to Mexico, from where drugs cartels transport them over the border and into the US.