More than 42 million illicit cigarettes have been seized or detected by customs officers in the North West in the last few months.
The cigarettes can contain unregulated chemicals
Surveillance operations have led to the prosecution of criminals responsible for £6m worth of tax evasion, HM Revenue and Customs office has said.
The office is warning the public that counterfeit cigarettes can be more harmful than legal varieties.
The cigarettes can contain levels of unregulated chemicals within them.
HM Revenue and Customs say the illicit tobacco trade robs public services of revenue and undermines honest businesses.
The money made in this way is often also used to fund other forms of organised crime.