The midfielder was axed following an internal investigation into an incident that occurred last month.
The 29-year-old is appealing against the decision, at a hearing which will be held next week.
Quakers are reluctant to shed any light on the matter, but the club admitted disciplinary procedures are continuing.
Darlington’s communications manager Martin Walker said: “We can confirm that a disciplinary issue concerning one of our players is currently ongoing, but it is a private matter which is being dealt
with internally, so it is not appropriate for us to go into any detail at the moment.”
Smith had been a regular in Steve Staunton’s side.
After the manager was appointed last October the leftsided player had been selected in the starting XI more than anyone else, missing only one game.
But his regular appearances came to a sudden halt in the middle of February, with the visit of Chesterfield being the first without the Middlesbrough- born player in the side.
He had formed a left-sided partnership with full-back Stuart Giddings who is another out of the team, though his absence is due to injury.
The defender is sidelined with a groin strain and misses tomorrow’s visit of Barnet.
Staunton does not expect him to return for at least another week while Richie Byrne is making good progress in his recovery from a hamstring strain.
Noel Whelan (hamstring) remains out, though he successfully came through a practice game on Tuesday.
But Chris Lumsdon (back) played in the same match and afterwards complained of stiffness. Staunton hopes to see Mark
Bower (ankle) return before the season ends.
The manager revealed both he and assistant Kevin Richardson have started contract talks with chairman Raj Singh.
Their deals expire at the end of the season, and Staunton said: “Myself and Kevin were speaking to the chairman a couple of weeks ago and we were discussing what we are going to do.
“There is no problem on our behalf, he’s the man in charge, it’s his call what he wants to do.
“But we’re certainly here for the fight and I know that the club needs stability. We need to keep it moving in the right direction.
“There’s a lot of good things happening behind the scenes, it’s very positive for the town and that’s why it’s important that we try and get the supporters to stay on board through these difficult
times and that we stick together so that we come out fighting next season, no matter what division we are in.”