Heroin addicts are being sold nutmeg by cheating dealers because of a shortage of the drug following the attacks on Afghanistan.

The deception could lead to more overdoses as the impure heroin is sold on the streets.

There are about 2,000 taking heroin by injection in Brighton and Hove, which has one of the highest overdose death rates outside London.

Charity workers said the number could rise because users sold mixed substances cannot gauge the correct dose.

The impact of the US-led attacks, which wiped out much of the opium production, is only now being felt on the streets because stockpiles from previous harvests maintained supplies.

Police warned that as prices rose from £60 a gram some addicts would turn to desperate measures to feed their habit.

Drug treatment centres are also expecting a surge in the number of people turning to them as a result of the war.

Rosie Brocklehurst, spokeswoman for the charity Addaction, said: "If there's a three-month waiting list fewer people will go in for treatment.

"We need to ensure the resources are in place to cope."