With league leaders Gainsborough Trinity Reserves in cup action, the third-placed Zebras had the chance to cut the gap as they hosted bottom side Louth Town.
But the script went awry early on when Robin Beecroft gave the White Wolves a first-half lead.
Brigg’s leading scorer Reece Moody levelled matters in the 35th minute with his 18th goal of the season, and Cameron Hill completed the turnaround a minute before half-time.
There was no more scoring in the second half despite Louth ending the match with 10 men following the dismissal of Dominic Hanton.
The result keeps Brigg in third place, four points behind Trinity with two games in hand, and a point behind second-placed Lincoln Moorlands Railway.
They now face a crunch fortnight as they host both of the sides who stand in their way of the league crown.
Moorlands visit the Hawthorns on Saturday with just one league defeat to their name this season, before Trinity come to Brigg on Saturday, March 9.
Kick-off for both matches is 3pm.