MacPherson's Saints were narrowly beaten by Celtic at Love Street

Shunsuke Nakamura appeared to be felled by St Mirren's Gary Mason on the edge of the penalty area, and then netted the resulting free-kick.

"Frustration is an understatement," said MacPherson to BBC Scotland.

"I have to be careful what I say, but in certain situations, we really need an explanation to what we see."

Interview: St Mirren manager Gus MacPherson

MacPherson has already been punished by the football authorities in Scotland for his outspoken views on refereeing decisions.

But following his side's narrow defeat at home to Celtic he said referees often make snap decisions too easily.

"I've watched it again in the video, and it's just too easy to give that decision," said MacPherson.

"There's no point in speaking to the referee, because we get the bog-standard answers from his angle and his opinion.

"We all understand how difficult it is at normal speed to make that decision, but it's the wrong decision.

"We were excellent, every single player in a black and white shirt stood up to the challenge.

"And I thought there were some outstanding individual performances as well."