Victory would have guaranteed Chester top spot and a home semi-final in the play-offs but the race for the championship now goes down to the final weekend.
Chester could have no real complaints about the defeat at Bury with the hosts taking full advantage of a slack start from the visitors.
Broncos opened up an 11-0 lead inside 20 minutes before the Gladiators woke from their slumber with an unconverted try from captain Mark Kingsley.
However, the home team moved further ahead with a converted try but hooker Billy Brickhill touched down on the stroke of half-time for the visitors, who went into the break 17-10 behind.
Chester made a perfect start to the second period with Johnny Rae crossing the whitewash to bring them within a point but that was as good as the afternoon got.
Bury picked holes in the defence to cross for two converted tries and although Joel Gibbs touched down for Gladiators, the hosts had the last word to inflict a third defeat of the season on Chester.