Philippe Clement has revealed a stern Rangers dressing room reminder left John Lundstram in no doubt over his mistake in being sent off against Celtic.

The Ibrox midfielder was shown a straight red card for a rash challenge on Alistair Johnston in the 2-1 loss at Celtic Park.

Lundstram was initially booked before Willie Collum upgraded the punishment to a red card after being advised to review the incident at the pitchside VAR monitor.

Clement said after the match that he had "no complaints" over the red card but branded the tackle "totally unnecessary".

The Belgian manager faced further questions on Lundstram at his press conference ahead of the Scottish Premiership fixture against Dundee on Tuesday night. 

And Clement confirmed he had held further discussions with Lundstram before revealing a dressing room board reminder put up for Rangers players clearly outlining their principles of play - which states tackles like Lundstram's should not be made.

The code of conduct was in place before the trip to Celtic Park with Clement accepting Lundstram had simply made a split-second mistake.

READ MORE: Ben Davies on John Lundstram red and Rangers' reaction to Celtic loss

In the press conference, quizzed on whether he had spoken to Lundstram, Clement said: "Yes but John spoke first to me to say sorry. He knew from the first second.

"He wanted to go for the ball because we were pressing high. If you can win that ball it can be a one-v-one situation and create a chance. He has gone a split second to late and connects with the foot instead of the ball in that moment.

"I don’t want to see those tackles from that far. He knows, it’s one of our principles, it’s on the board in the dressing room.

"Players made mistakes, managers make mistakes and even sometimes journalists! Lunny has been giving a lot and that’s why I said after the game.

"In the last months was he always the best player? No. Did he have bad games? Yes. But he is giving his best and wants to for the club. He made a mistake and it’s now looking forward."