Tonga triumphed in Aberdeen as Scotland slumped to a miserable 21-15 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 slumped 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.
Apikotoa missed an early penalty from 45 metres before kicking a second from in front of the posts after Scotland killed the ball and a Laidlaw penalty attempt careered back off the post before he kicked Scotland level after 11 minutes.
Tonga continually infringed and referee Mathieu Raynal lost patience when Lokotui obstructed Richie Gray at a lineout and was sent to the sin-bin. Tonga's short-handed scrum were penalised and Laidlaw's kick was successful to give Scotland a narrow half-time lead.
Laidlaw kicked a penalty to extend the lead to six points, but Tonga kept up the pressure and their 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 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.