The Junior All Blacks against won an error-strewn display in their final match of the Pacific Nations Cup against Tonga.

The New Zealanders had already wrapped up the championship before taking the field in Suva and outscored Tonga by seven tries to three but were helped when Tonga had two players sent to the sin bin in the second half in their 47-25 win.

The result maintains the Junior All Blacks' perfect record in the competition and left Tonga without a win.

The Junior All Blacks allowed Tonga to open up a 10-0 lead following an early try from Alipate Fetafehi before quick tries from Hosea Gear and Ryan Crotty saw the New Zealanders claim the lead after 25 minutes.

Tonga responded to take a 20-12 half-time lead following a try from Muli Kaufusi, but another quick brace this time from wing Rene Ranger and loose forward Sione Lauaki saw the Junior All Blacks regain the lead.

After Tonga added a third try through wing Matteo Malupo to move within one they had Mahe Fangupo and Malupo sent to the sin bin.

And Alby Mathewson scored the fifth try to add to the lead before replacement back Robert Fruean and Gear, with his eighth try of the tournament, sealed the win with late tries.