Nearly two tonnes of illegal hand-rolling tobacco was seized in Wales during summer 2015 thanks to a Welsh Government-funded project.
"Operation Fetch" was a Wales-wide initiative in which local authorities worked with tobacco sniffer dogs to find illegal tobacco.
The supply of illegal tobacco has the potential to undermine work in Wales to reduce smoking rates and compromise a range of tobacco control measures, including age-of-sale legislation, labelling and the tobacco display ban.
Trading Standards officers worked with the providers of tobacco detection dogs, which lead to the seizure of:
" Almost half a million illegal cigarettes;
" Nearly two tonnes of illegal hand-rolling tobacco - enough to make two million roll-your-own cigarettes.
Smoking is the biggest single cause of early death in Wales, claiming the lives of almost 6,000 people every year. Most new smokers in Wales are under 18 and an estimated 11,000 children start smoking every year.
Illegal cigarettes are often supplied singly, increasing their accessibility and affordability and making illegal tobacco a highly-effective means to recruit new smokers among children and young people.
Minister for Health and Social Services Mark Drakeford said:
"I am very concerned about illegal tobacco because its affordability and availability threatens the health of children, making it so much easier for them to access tobacco. It also eliminates the price incentive for smokers to quit the habit.
"This is not a Robin Hood crime. It is criminality which deprives the public of vital revenue which is used to fund essential public and health services, including tackling the damaging impacts of tobacco itself but its effects extend far beyond that.
"We are determined to bear down on this illegal trade and safeguard public health. I would like to take this opportunity to commend all those involved with Operation Fetch and their endeavours to halt the trade in illegal tobacco."
Matthew Cridland, the chair of the Wales Heads of Trading Standards, added:
"Figures show 15% of the tobacco consumed in Wales is illegal. That's the equivalent of one million illegal cigarettes being smoked in Wales every day. The prevalence of illegal tobacco at this level presents a serious threat to health by undermining all of the controls designed to reduce consumption and prevent children from accessing tobacco.
"Because of this, tackling illicit tobacco is a key priority for Trading Standards in Wales. The results achieved in Operation Fetch are really encouraging and demonstrate the commitment of Trading Standards to this challenge.
"We want to work with all tobacco control partners to address not only supply but also demand for illegal tobacco and Trading Standards will continue to vigorously pursue all those who distribute and supply this product."