The visitors' frustrations were then compounded as Shaun Williams' delightful strike decided a match that had meandered up until that point.
MK Dons manager Karl Robinson also admitted he did not think Chambers' challenge was worthy of a free-kick.
Smith said: "It was a nothing game - we had one good chance from Sam Bantom but it didn't look like it was going anywhere.
"Then a decision that has been made changes the course of the game and then we got a bit of fire in our bellies and finished the game really well.
"Unfortunately, you can only control so much and we've had two decisions go against us that have cost us the game.
"I don't think either team got it going and while they had the lion's share of possession, they weren't really hurting us.
"The last 20 minutes was more what we're about in terms of driving forward and taking the game to teams, but up until then we weren't doing enough of that."
- Sports & Recreation
- Ashley Chambers
- Patrick Bamford