Halsey adjudged Ciaran Clark to have fouled Ashley Young in the sixth minute, though there appeared to minimal contact, and McLeish felt it should not have been given.
“I didn’t think it was a penalty I thought Ashley threw his leg in to Ciaran Clark’s leg," he told reporters.
"Ciaran was static, he planted his leg firmly on the ground and in actual fact when I saw the replay he then tries to pull his leg away so I don’t think it was a penalty.
“It’s hard to say to the ref that he totally got it wrong but it’s a split second for them and i think it's a difficult job. I certainly felt it was a very soft decision.
“The game’s played at such a fast pace at this level the little one-touch football is often quicker than the human eye and we feel a little bit aggrieved at some decisions in the last few weeks which aren’t in our control.
“You can play the best game in the world but still lose because of things not in your control.”
The Scot expressed his belief that the Villans made a bright start to the game but insisted the early penalty and goal knocked the stuffing out of his young side.
“It knocked them back a mile. Having said that I’m proud of the young players that played today," he continued.
"They stuck gamely to their task but they gave away a couple of goals a wee bit softly, especially the second, that was a blow."
Despite the defeat, which leaves Villa perilously close to the relegation zone, McLeish is confident his team will stay in the Premier League.
He said: “I believe we will be OK we’ve got three huge games coming up and these are crucial for us and we’re looking to the experienced guys to help the younger lads to deal with these huge games.”
“The last two seasons are just not good enough for Aston Villa’s name in this game.”