She told how the cannabis was sourced by Mr Brundell in the North Island and transported to Leech in Dunedin, "sometimes by car, sometimes by public transport, and in the later stages, by a paid courier."
Leech then sold the drugs from his Dunedin home where he lived with his young daughter.
Justice French said: "You packaged the cannabis when it arrived into smaller amounts and sold it from your home in the form of tinnies ($25), ounces ($350-$400) and pounds ($5000-$5600). You would then forward some of the money back through bank accounts of various associates."
Police enquiries found 90 cash deposits between August 2007 and May 2011 but failed to trace all of the recipients.
When caught by police, Leech admitted his role in the operation, but "offered no explanation."
Justice French said that Leech - who has six previous cannabis-related convictions, including one for cultivation - was a "good father" despite his illegal activities.
She said: "The information tells me that you are 37 years of age, a beneficiary with five children. You only became a beneficiary because you took on the care of your youngest daughter. Her very positive school report suggests you are at least in some aspects a good parent."
Justice French jailed Leech for three years and also made forfeiture orders for his car and some cash that was found in his possession when he was arrested.
Last month, Leech pleaded guilty to claiming almost $53,000 in benefit payments he was not entitled to after failing to inform Work and Income about the large sums of cash he was earning from drug dealing.
He told investigators he did not disclose the income because it was from illegal activities.
At Dunedin District Court, Leech admitted four charges of dishonestly using Work and Income documents for financial gain and one charge of wilfully failing to disclose his correct financial circumstances to the Ministry of Social Development between August 3 2007 and June 16 this year.
Judge Stephen O'Driscoll convicted Leech on all charges and remanded him in custody for sentence on November 10.