Dozens of suspected slaves have been rescued in a week-long crackdown on illegal drug gangs across Britain that uncovered hundreds of vulnerable children, according to UK officials.

Key points: Thousands of children are thought to be used to carry drugs from cities to rural areas

Thousands of children are thought to be used to carry drugs from cities to rural areas 364 children at risk of exploitation by drug gangs were protected in this latest bust

364 children at risk of exploitation by drug gangs were protected in this latest bust 500 men and 86 women were arrested as suspects

More than 500 people were arrested in raids that saw $AU579,000 in cash, $AU324,000 worth of cocaine, as well as significant quantities of crack cocaine and heroin seized in a major coordinated police action.

"We know that criminal networks use high levels of violence, exploitation and abuse to ensure compliance from the vulnerable people they employ to do the day-to-day drug supply activity," said Nikki Holland from the National Crime Agency (NCA).

"There are now fewer drugs on the streets, more vulnerable people safeguarded and the public can be reassured that collectively we are committed to tackling serious and organised crime offenders."

Thousands of children in Britain, some as young as 12, are thought to be used by so-called "county lines" gangs to carry drugs from cities to be sold in rural areas.

Some victims are initially groomed with flattery and gifts, and many are trapped in the trade by debt bondage or threats of kidnap, violence and rape, the NCA said.

More than 30 suspected slaves were offered help under the government's National Referral Mechanism and 519 adults and 364 children at risk of exploitation by drug gangs were protected in this week's crackdown.

The NCA told the BBC that these children could be dealt with in a number of ways, including being returned home if missing, referred to local services, referred to the National Referral Mechanism — which identifies victims of human trafficking — or placed under a protection order.

A total of 500 men and 86 women were arrested as suspects. Nearly 50 weapons were found including guns, swords, machetes, an axe, knives, samurai swords, and a crossbow.

"This is clearly a big problem and it's good that it has started to be taken seriously," said Jakub Sobik from Anti-Slavery International.

He said more work needed to be done to ensure that young people snared by drug gangs were consistently treated as victims and not criminals.

"Most cases start with nice things like gifts and the promise of a glamorous life but it very quickly turns into a nightmare that children simply can't get out of because their lives start to be controlled by criminal gangs."

Gangs often tell children they will not be punished if they say they were coerced, citing a legal defence in the Modern Slavery Act meant to protect victims of human trafficking who are forced to commit crimes, police said.

ABC/Reuters