Human excrement, asbestos, mould and dead flies have been discovered in cigarettes being smoked regularly in Britain, the Daily Mail reported.
Investigators working for the tobacco industry spent weeks rummaging through litter bins for cigarette packets to assess the scale of the black market.
They found that about one-third of packets contained fakes or cigarettes brought in by smugglers.
The UK Border Agency has also intercepted items containing asbestos, mould and human excrement.
A haul in Derbyshire found cigarettes made from the remains of crushed flies.
MS Intelligence carried out the research on behalf of a number of cigarette companies who are concerned that plans to introduce plain packaging will help black market tobacco barons flood the market with fakes, the daily said.
Analysts collected 13,000 packets in Birmingham between April 3 and May 11.
The Daily Mail said that most of the bogus brands originated predominantly from China, and some packets were almost identical to the real thing.