They went into the last league game of the season against neighbours Burscough needing to earn all three points in order to stand any chance of finishing in second spot.
This they achieved but Skelmersdale United – who held the second spot and Wythenshawe Town in third place with a better goal difference – also won on an afternoon of high drama.
Charnock opened brightly and almost took the lead when a rising drive by Brad Carsley thundered against the underside of the crossbar but their endeavours were rewarded on 18 minutes when Carl Grimshaw fired home confidently past the advancing Mason.
Charnock were looking for a second goal and almost got it on 36 minutes when Luke Gibson’s snap shot clipped the top of the crossbar. The home side missed a golden opportunity early in the second half when Grimshaw fired wide from a good position following a neat flick-on by Carsley.
The visitors kept plugging away and got their equaliser on 63 minutes when a free kick by full-back Luke Denson from fully 25 yards out on the left flew into the top corner.
With 10 minutes remaining, Charnock regained the lead when Grimshaw planted a firm header into the net from a fine cross by Jack Gooden from the left.
Charnock finished the league season in fourth place. They start their Macron League Cup campaign at home tonight (7:45pm) against Ashton Athletic.