With the second placed Ospreys playing the touring Canadians, the North made the most of their opportunity with a consummate 17-0 success against bottom side the Dragons at Merthyr RFC.
Openside flanker Tom Young kicked off the scoring with a try and Sam Campbell followed up with a second which Joseph Griffin converted.
Owain Shepherd added a third try after the break and though they failed to pick up a bonus point, with four games remaining they find themselves seven points ahead of their nearest rivals.
The Blues South were unable to make it a double for the region – they went down 26-24 to the Scarlets.
Elliott Jones crossed for a brace of tries for the Blues and Diggy Bird weighed in with a try, penalty and three conversions.
However, tries from Kirby Myhill, Jamie Kaijacks, Lawrence Reynolds and Dyfan Dafydd earned the Scarlets a crucial victory which keeps alive their chances of reaching the final.
