More than 26,000 illicit cigarettes were seized in raids on seven shops in Leeds.
West Yorkshire Trading Standards teamed up with police to target the sale of counterfeit and tax-dodging tobacco products at retailers in Harehills and Armley.
Using sniffer dogs they found goods hidden behind false walls, in secret compartments and kitchen units and at the back of shelves behind the counter.
As well as the cigarettes, the dogs detected 10kg of illicit hand rolling tobacco. In total, the seizures had a street value of £7,000.
Investigations are ongoing.
The raids coincide with Mouth Cancer Action Month this month.
Coun Pauline Grahame, deputy chair of the West Yorkshire Joint Services Committee which oversees the work of Trading Standards, said: “There are fears that the widespread availability of illegal tobacco products will undermine efforts to reduce smoking prevalence by making smoking more affordable and accessible.
"We know that most smokers want to give up smoking but their quit attempts are really undermined if somebody offers them a cheap supply of tobacco. It’s also really worrying that children are being targeted by unscrupulous dealers.”
David Lodge, head of West Yorkshire Trading Standards, added: “Smoking rates in the UK are declining.
"Reducing the supply and demand of illegal tobacco is one important element of a comprehensive approach to tackling tobacco harm in communities.
"It is key to addressing smoking-related health inequalities and poverty, playing a key role in preventing young people from starting to smoke."