Scrutiny of Celtic’s manager has increased after a draw against Dundee United was followed by defeat at Falkirk.

The club’s domestic form had previously been almost flawless, apart from a loss to Rangers. Celtic remain top of the league, but supporters are concerned their lead is precarious and are questioning the direction of the club.

Hart, a former Parkhead goalkeeper, said such scrutiny was always part of managing Celtic and did not change O’Neill’s standing with the support.

Hart said: “It’s flak with love, and that doesn’t make any sense. Of course, we know it doesn’t make any sense, but Martin O’Neill will be, and is, absolutely adored. But he knows what he signed up for as a Celtic manager, and he would expect to be getting a lot of questions asked about him.

“And that’s not saying he’s not up to the task or he’s not the man for the job, but that’s what comes with the territory. If you really understand Celtic, you understand that if you’re not borderline perfect domestically and challenging in Europe, you’re going to get it.”

Hart said the strength of feeling also reflected a wider disagreement between supporters and the club’s board.

Hart said: “You’re going to get it because they care and they’re intelligent football fans. And, there’s a massive disharmony with the board. The fans really don’t understand what the direction of the club is. And obviously the board have got their opinions in terms of the success that they had and continue to have.”

He said winning had previously eased similar concerns after O’Neill returned to the club and results improved.

Hart said: “So, it is difficult. That was really shining brightly mid-season last season, but then Martin came back in and the team started to win and it goes away. It’s amazing what winning can do, and at the moment they’re not.”

Hart also described the mood around Celtic’s match against Besiktas as a concern, saying supporters appeared resigned rather than angry.

Hart said: “They had a difficult result at Falkirk. I think they drew at home to Dundee United. And then this Besiktas game felt ominous. It felt like there was going to be a riot, or not even a riot. Do you know what the worst feeling you can have in a stadium is? And I very rarely felt it up there. It wasn’t anger, it was people going, ‘Pfft, we lost again.’ That is the worst feeling you could have.”

He said Celtic’s position at the top of the table meant the situation was different from other managerial pressures, and suggested the next league match could help change the mood.

Hart said: “If they can take the atmosphere that they generated towards the end of the game last night into the league game this weekend, I think it’s Kilmarnock, then it could be a massive spark to go again.”