Home Office minister Jeremy Browne said the worst cannabis is now about six or seven times stronger than it was a generation ago.
He said: "It's like somebody going from drinking a pint of beer to drinking a pint of neat vodka."
He added that despite falls in heroin use, he was concerned about new threats.
Mr Browne said: "Some of these legal highs can be very dangerous for people's health and of course the situations is mutating the whole time. All of these chemical compounds, these synthetic drugs, are being manipulated."
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Penalties of £100 or a court fine of up to £1,000 can now be handed to anyone caught lighting up in a private vehicle with someone under 18.
Bodies are being buried in backyards and overwhelming morgues as officials try to find another plot of land to lay them to rest.
Authorities have warned that the death toll is likely to rise as much of the building is yet to be searched.