Illegal cigarettes could be filled with human excrement, dead flies and asbestos, consumers are being warned.
The Local Government Association (LGA) says people should “think twice” before purchasing cigarettes from the black market as all three have been found in counterfeit cigarettes before.
The LGA said fake cigarettes also pose a fire risk, damage legitimate businesses and cost the UK economy about £3 billion in unpaid duty annually.
Authorities have seized thousands of illegal cigarettes in Wolverhampton, Bristol and Nottingham in an effort to stamp out the trade.
Officers from Trading Standards say they have found fake cigarettes hidden inside vacuum cleaners, under floorboards and in toilet cisterns.
Some have contained asbestos, mould, dust, dead flies, rat droppings and human excrement. Many feature much higher levels of toxic ingredients such as tar, nicotine, carbon monoxide, lead, cadmium and arsenic than genuine cigarettes.
Councillor Joanna Spicer, vice chair of the LGA's safer and stronger communities board, said: "Counterfeit tobacco being sold cheaply through the black market by rogue traders is hampering council efforts to reduce smoking. This illicit trade is also funding organised criminal gangs, damaging the livelihoods of honest businesses and costing taxpayers billions of pounds a year.
"People buying cheap cigarettes might think they are getting a great deal - but the truth is that they're not. If they knew what they might contain, they might think twice about buying them."
Additional reporting by PA