Bill Hughes, director-general of the Serious Organised Crime Agency, said gun crime, drugs and people smuggling are heavily linked to overseas gangsters.
He told MPs on Tuesday: "Most of the crimes we are dealing with are international. The source of the trouble starts elsewhere."
His comments came as Sir Stephen Lander, SOCA's chairman, warned that large-scale "cannabis factories" run by Vietnamese and Chinese criminals are springing up across the country. "
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