Aston Villa boss said Stephen Ireland needs to pull up his socks and get with the game.
Houllier, who was speaking after the goalless draw against Birmingham at the weekend, said "He (Ireland) needs to do much harder.:
Ireland did not play at the weekend.
"He played against Chelsea and did well but against Sunderland he was not good enough for me. Simple as that.
"Skill is one thing but you need to compete as well," Houllier said.
Ireland, 24, was rated $12 million during the summer but Houllier feels he hasn't been proving his worth just yet.
Houllier said: "It's a difficult period for him but the club will support him in that. He's come to a new club and then has a different manager.
"We know he is a good player, although I don't want to have someone who you say 'He is a good player... but he loses too many balls'. He needs to get rid of the buts about him.
"He needs to work harder, his touch of the ball, his defensive effort."
Bog bodies are kings sacrificed by Celts