TNS missed the chance to open up a bigger gap on Rhyl at the top of the table as they went down to a single goal defeat at Farrar Road.
The Saints went into the late kick-off knowing that the Lillies had lost 2-1 at lowly Llanelli, but they failed to take advantage as they gave a jaded display in a scrappy affair of few chances for either side.
With the game evenly balanced, Paul Roberts settled matters in the Citizens' favour with a first-time volley after 69 minutes that beat keeper Ged Doherty just inside his post.
Saints tried to raise their game, but John Lawless could only fire wide after a surging run and cross from Chris King and sub Marc Lloyd-Williams miscued badly when attempting to convert a right-wing cross.
The first-half hardly produced an incident of note, apart from Michael Wilde hitting a post with a shot from inside the box, as both sides were restricted to long range efforts.
But the best chance of the game fell to Roberts early in the second-half when he was put through by Kevin Scott but could only fire weakly straight at Doherty.
It was pretty poor fare for the S4C television viewers and the late kick-off and rival FA Cup attractions on BBC1 produced a poor gate for a game that would have attracted a good crowd under normal circumstances.

Bangor City v TNS match report, photos and stats