Paul Lambert has accused Moi Elyounoussi of "letting the great Jock Stein down" after the Norwegian international was caught on his phone during Celtic's shock Europa League defeat to Sparta Prague.

The Hoops fell to a 4-1 loss at Parkhead on Thursday and during the late stages of the match the BT Sport cameras caught Elyounoussi on his mobile.

The 26-year-old has since apologised saying: “First of all, this is unacceptable from me.

"I have talked to both the coach and the captain and the case is dead between us.

“The phone is just out of pocket. I have warnings from Milan-Lille, the second match in our group, and I just wanted to check the result in that match.

“In any case, it is stupid of me to put myself in that situation. I lie down and take the punishment I’ll now possibly get.”

But Hoops hero Lambert believes the damage has already been done.

He told BBC Sportsound: "If you don't change the players, sometimes they will change you.

"There's something obviously wrong if Neil said that [about changing the culture].

"We played in an era where we were very strong.

"I look at the lad Elyounoussi on his phone and you are letting the great Jock Stein down, you are letting the Lisbon Lions down.

"That will absolutely rile him, because I know the way Lenny was as a player.

"You are letting your team-mates down, they are out there getting a chasing.

"You have to get the ones out who you think are going to let you down.

"I don't know all the Celtic guys, I only know Scott Brown, the lad [Callum] McGregor, the good guys who will run through a wall for you.

"But if they are not, then you have to move them on.

"If that is the case he has to move them, or they will change you.

"The football club is too big to accept that, they don't have a divine right to win everything.

"If there are factions and disharmony in a dressing room then it is a really dangerous thing."