The Hoops hierarchy are under intense scrutiny after vowing to learn from last season's mistakes
Paul Lambert insists Martin O'Neill won't take no for an answer as pressure mounts on Celtic to strengthen their squad this summer.
The Hoops hierarchy are under intense scrutiny after vowing to learn from last season's transfer mistakes, which culminated in a calamitous Champions League exit to Kairat Almaty.
Principal shareholder Dermot Desmond pledged to back O'Neill with a hefty transfer kitty after the Double-winning boss signed on for another year. But the champions have yet to spend a penny, leaving supporters fearing another chaotic transfer window.
However, Lambert believes O'Neill won't be afraid to speak his mind by demanding the quality he needs to retain the title and reach the Champions League promised land.
He told Record Sport: "I don't think Celtic as a club stands still at any point. I'm pretty sure the people in the hierarchy like Michael Nicholson and Dermot won't stand still, especially when the manager's there. The manager won't like that to happen again, that last season syndrome. I don't think anybody at Celtic wants that.
"I'm pretty sure everybody's learned their lesson that you can never take your eye off the ball, you can never take your foot off the gas, you have to go and win it again. And that's the beauty about Celtic, you have to keep winning it, it doesn't matter. That title's gone now, that's in the history books, you have to go and do it again.
"Whether Rangers and Hearts are stronger, I don't know, but I'm pretty sure Celtic will be a lot stronger than they were last year. I know how management and board-level works because I was a manager myself for 20 years. "They'll talk and have dialogue between Martin, Michael and Dermot, I'm pretty sure. I don't know what parameters they'll go with but to make a mark in Europe, then they're going to have to go a good bit anyway, that's for sure.
"Domestically is so important for them but if you can get into the Champions League, you don't want to be getting into that with one arm tied behind your back. If there's any manager that will get his way, it'll be him. That's the beauty of him, because he'll not take it easy if he's not going to get it.
"So I think you'll have good dialogue and that's why I think Celtic won't make the same mistake again."
Lambert - who was handed the captain's armband during O'Neill's iconic first spell 25 years ago - believes his former boss will have sought certain assurances before accepting the job.
The ex-Aston Villa manager said: "I worked under him for five years and we had him in his pomp. We would run through walls for him at that time.
"He inherited some brilliant footballers and he brought in lads to help. He knew exactly what he wanted and who he wanted. I don't think that will change.
"I think that will be in him that he wants to be successful, he wants to make a mark in Europe, and all those sorts of things.
"He won't have changed. The only thing he's changed is his age, but he won't have changed the way he is as a person, and his drive to win games."
While Rangers have already added five new faces and Hearts have brought in eight, the only movement at Celtic Park has been 12 departures.
Lambert added: "I think due to the World Cup as well, and I know it's an easy answer. I don't know who Rangers and Hearts have brought in, but it depends on the type of player that Celtic are going for.
"Are they established World Cup players? Or are they playing for countries or are they Scottish guys? I'm not so sure, but maybe they're waiting for that time.
"But I'm pretty sure after what happened last season, I don't think they'll be sitting on their hands here, that's for sure."