Two men were arrested and a loaded gun was seized in Plaistow as part of a nationwide crackdown on county lines drug dealing.

More than 140 weapons, including guns, axes and swords, were seized in targeted raids last week, along with more than £200,000 in cash and stashes of heroin and cocaine, the National Crime Agency (NCA) said.

The operation, which included the execution of warrants and visits to vulnerable people at risk of having their homes ‘cuckooed’ - taken over by dealers to sell drugs from - also resulted in more than 600 arrests.

Initial figures show more than 600 children and 400 vulnerable, often drug-addicted, adults were assessed for “safeguarding purposes” while 40 people were referred as being potential victims of human trafficking and modern slavery.

The agency highlighted the vehicle stop by armed police in Plaistow, where officers arrested two gang members with county lines link and seized a loaded 9mm fully automatic weapon, as an example of the type of activity it was carrying out between January 21 and 27.

Other cases around the country included the discovery of a 15-year-old boy, missing from Liverpool, at a property in Aberdeen where wraps of crack cocaine and heroin were also found.

Around 10 per cent of the known 2,000 lines in the UK are “associated with serious violence” but this figure is “probably under-reported”, according to Duncan Ball, the National Police Chiefs’ Council lead for county lines.

He added: “Last week’s targeted work on county lines gangs shows how police forces across the UK are working together to dismantle these networks and protect the young and vulnerable people who are exploited by them.”

County lines is a drug distribution model which typically involves city gangs branching out into smaller towns or rural areas to tap into new markets.

They deploy children and vulnerable people as couriers to move drugs and cash between the new market and their urban hub.

It is estimated by the NCA that the networks can net UK gangs around £500 million per year.