Tonga triumphed 21-15 in Aberdeen as Scotland slumped to another miserable loss which is sure to pile pressure on head coach Andy Robinson.
Tries from Lua Lokotui and Fetu'u Vainikolo and 11 points from the boot of Fangatapu Apikotoa earned Tonga a memorable win at Pittodrie.
Greig Laidlaw kicked five penalties for Scotland, who were blunt in attack, as Robinson's men fell to a third defeat of the EMC Test series following losses to New Zealand and South Africa.
It was an attritional affair on a narrow pitch which limited space and, once again, Scotland's passing lacked the accuracy required as the ball hit the floor with alarming regularity.
Scotland lacked ideas to overcome their physical opponents, who had three players sin-binned but were deserved winners as the hosts tasted defeat in Aberdeen for the first time.
A season which featured early World Cup elimination and a RBS 6 Nations wooden spoon was revived by the June wins in Australia, Fiji and Samoa before New Zealand and South Africa inflicted defeats which will see Scotland outside the top eight seeds for the 2015 World Cup draw.
Assuming he is retained, Robinson will next enter his fourth Six Nations, beginning with the Calcutta Cup at Twickenham, needing a remarkable turnaround to avoid another abject spring showing.
Due to a mixture of choice and circumstance, change was required for the final match of 2012, with six alterations from the XV which began the Springboks Test.
Making their first starts were scrum-half Henry Pyrgos and loosehead prop Kyle Traynor, who was released by Edinburgh in the summer but brought in due to decimated front-row resources.
Hooker Scott Lawson, lock Alastair Kellock, flanker Alasdair Strokosch and centre Max Evans also started.
Tonga lost to Italy and beat the United States this month and featured a host of European-based players eager to claim another northern hemisphere scalp following their World Cup win over France in the third Test between the sides.
Scotland were bidding for a morale-boosting win, just as they claimed in 1995 and 2001, but fell behind early on.
Apikotoa missed an early penalty from 45 metres before kicking a second from in front of the posts after Scotland killed the ball.
A Laidlaw penalty attempt careered back off the post before he kicked Scotland level after 11 minutes.
Tim Visser and Sean Lamont stretched Tonga down the left and a period of concerted pressure followed.
Scotland piled over the line, but it was impossible to rule whether the ball was grounded beneath a heap of bodies.
Scotland struggled to breach the Tonga defence until a gap presented itself to Laidlaw and he took it.
The fly-half ran 30 metres towards the Tonga line, with Visser on his left shoulder, but marked, and Strokosch on his right.
The flanker fumbled Laidlaw's pass as defenders recovered, the danger brought to an end.
Tonga continually infringed and referee Mathieu Raynal lost patience when Lokotui obstructed Richie Gray at a lineout and was sent to the sin-bin.
Prop Halani Aulika was fortunate not to join him after body-checking Matt Scott, with no attempt to tackle using his arms.
Tonga's short-handed scrum were penalised and Laidlaw's kick was successful to give Scotland a narrow half-time lead.
Scotland continued to struggle with ball in-hand, a Lamont carry deep into the 22 one of the few occasions the hosts breached enemy lines.
A penalty followed which Laidlaw kicked to extend the lead to six points, but Tonga kept up the pressure.
Apikotoa missed the chance to reduce the arrears, but Tonga's persistence paid off when they spread the ball wide and Lokotui made amends for his earlier indiscretion by burrowing over. Apikotoa converted to put Tonga 10-9 ahead.
Laidlaw kicked two more penalties to give the hosts a five-point lead entering the final quarter, but the advantage crumbled all too easily.
The ball was spread wide to Vainikolo, who simply stepped up the pace and ghosted down the left, evading substitute Nick De Luca, to score.
The conversion was missed by Apikotoa and Bath fly-half Tom Heathcote came on for his debut.
Nili Latu became the second Tongan sin-binned 11 minutes from time for leaping on top of a maul, but Heathcote's resulting penalty was short.
The task became tougher for Scotland when Apikotoa kicked his third penalty to leave the hosts requiring a converted try to win with six minutes left.
Sione Timani was sin-binned, temporarily reducing Tonga to 13 men.
Latu returned, with an attacking scrum for Scotland as the game ticked into added time.
Scotland nudged forward, but captain Kelly Brown lost control at the base of the set-piece and Tonga scrambled clear.
The last act of the game was Heathcote dropping a Rory Lawson pass as Scottish players stood crestfallen - and defeated - across the pitch.