Town boss Nathan Jones was disappointed with his side's performance as they slipped to a 2-0 defeat to Chesterfield.
Joe Rowley scored from close range after 19 minutes before Jak McCourt fired in from the penalty spot after James Justin was deemed to have brought down Zavon Hines six minutes later.
The result sees the Hatters' lead at the top cut to three points, after second placed Notts County drew 2-2 with Lincoln City.
Jones said: "I am disappointed, I think it was a disappointing performance. I am not taking anything away from Chesterfield, they were better than us in the first half and that was when the game was won. We talked about it not being another Port Vale in terms of getting a foothold in the game, coming out and pressing high and working hard and we didn't do it.
"We didn't press high, we didn't set the tone, we didn't get on second balls and they were better than us first half. They switched the play, their goal was coming from their point of view and they scored a very good first goal. For us we were nowhere near in terms of our performance, out of possession and what we did, and we paid for it.
"I can't categorically say it's not a penalty. There's a little bit of contact – a hand on the back – it was far less than the contact down here in front of the press box with Sid Nelson and Elliot Lee. So how he doesn't give it, we're disappointed.
"It might have been the gamechanger, but I don't think we looked like actually scoring today. We had a few powder-puff shots. We didn't have any real kind of play, we didn't really test the keeper enough until we brought Jordan Cook on and he gave us something of note."