Research by the charity has found that the force made 2,775 arrests of children aged 17 and under last year, down from 9,779 in 2010.
Across England and Wales, the total number of arrests has fallen by 64 per cent in six years – from almost 250,000 in 2010 to 87,525 in 2016.
Frances Crook Chief Executive of the Howard League for Penal Reform, said: “For the sixth year running, we have seen a significant reduction in child arrests across the country. This is a tremendous achievement, and we will continue to support police forces to develop their good practice and reduce the number to an absolute minimum.
“Lancashire Police should be applauded for their positive approach, and the Howard League is proud to have played its part in a transformation that will make our communities safer. We are ensuring that tens of thousands of children will have a brighter future and not be dragged into a downward spiral.”
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Every police force in England and Wales made fewer child arrests in 2016 than in 2010. All but four forces brought down their number of arrests by more than half.
Nationwide, there were 703 arrests of primary-age children (10- and 11-year-olds) in 2016, a reduction of 18 per cent from the previous year.
The statistics have been published in a Howard League briefing, Child arrests in England and Wales 2016, which shows how reducing the number of children entering the system has stemmed the flow of children into custody.
Between 2010 and 2016, the number of children in prison in England and Wales fell by 58 per cent. The Howard League for Penal Reform has led a long running campaign to reduce the number of children taken into long and short term custody.
Nobody from Lancashire Police was available to comment