Martin O'Neill today warned Celtic need significant investment before they will be taken seriously in European football.
O'Neill believes his club are more than capable of coping with the demands of domestic football - but need new players if they are to have any hope of re-establishing themselves as a major force in continental competition.
"I'd like to strengthen the side," he told BBC Radio 5 Live's Sportsweek show.
"If we are trying to be serious contenders in European football, we have to have the necessary squad to cope with that.
"The squad is perfectly adequate for domestic competition, but perhaps not if you want to compete in European football.
"Every team wants to not only qualify for the Champions League, but also do something in it.
"It was brilliant to be involved in the Champions League this season, which was an absolutely sensational experience."
PA