Jack O'Connor shuffled out of Montrose studios on Monday evening a chastened man. The country's most powerful trade unionist had played dirty with Pat Kenny, branding his Dalkey home a 'trophy house'. As soon as the words had left his lips, he knew it had the potential to backfire in his face.

O'Connor's smart alec swipe at Kenny, which drove the broadcaster to use a rare expletive on live television, might have been met with gasps of satisfaction from his grass roots supporters who squirm at the lavish salaries paid to RTE stars.

But for a man whose public image has lurched from dull to dire in recent months, it was not a wise move and he knew it. Like a scolded puppy, he backed down instantly, said sorry, and, still feeling remorseful after a night's sleep, sent a second apology the following morning.

SIPTU's ultra-defiant leader had melted away, and in his place we saw a man capable of eating his words and admitting he was wrong. What the mandarins in the Department of Finance would give to see that side of his character again.

But close associates of Jack O'Connor say that day may come sooner than we think. The last year has been extremely difficult for him on many fronts, not least because he has let the side down in public and embarrassed his media-conscious fellow trade unionists by going out on a limb and appearing out of kilter with the economic reality and the public mood.

Then there is his grasp of the complexities of the current fiscal situation or, as some believe, his lack of it. On the RTE Frontline show last Monday, he got into a muddle over his own position on public sector pay cuts and was ridiculed by the audience for his indecision.

During radio and television interviews, his bulldog militancy is ever present but beyond the soundbites ('free market fundamentals' and 'race to the bottom' are his perennial favourites), he often stumbles, gets mixed up and comes across as confused when he is quizzed on the facts and figures.

Communications consultant and radio presenter Anton Savage recalls being aghast at O'Connor's sheer lack of information when he interviewed him last year on Today FM.

"SIPTU had just brought out a ten point plan but he was very sketchy on the detail and it was clear that he was discussing things that were way out of his comfort zone," he says.

"We were talking about fairly technical issues such as bank bond purchases, but he didn't seem to have an understanding of the subject, asking me to answer questions I had posed to him.

"Then again you could ask whether it is the job of an union leader to formulate macro economic policy. If you're one of those workers who's losing your job and taking a pay cut, and you see Jack O'Connor out there making life difficult for those taking the money out of your pocket, I can see there is a contingent who would regard that as very positive."

But the SIPTU president is also increasingly anxious about the fact that he is now widely accused as the man who could paralyse the economy and lead the IMF to take charge of its crippled purse strings.

He might have the neck of a bull but he is not immune to the growing criticism that portrays him as a deluded bully at best and a national hate figure at worst.

"A lot of people go around condemning him who have never met him," says a close acquaintance from the world of industrial relations.

"Jack doesn't have a very solid grip of economics and when he's put up against a university lecturer, he is at a distinct disadvantage.

"He's taking a very traditional trade union stance at the moment, marshalling his troops, presenting them in good battle order and seeing whether they can make a deal or not.

"But you have to look back on his track record. He and SIPTU have gone in for so much posturing and huff and puff over the last few years. The number of times they have threatened and balloted for strikes out at Dublin Airport in the last decade is legion. In those ten years, I think we have seen about two hours of disruption.

"He is a very honourable guy but he takes an awful lot on his shoulders. He is hugely popular with rank and file activists and has the biggest majority of votes in SIPTU ever. More people voted for him in Ireland than any other single person bar Mary McAleese.

"Yes, he is morose and always a little bit gloomy. Let's just say he's not on the happy side of life. He burns the candle at both ends. The only holiday I've known him to take was to Cuba.

"And he is a desperate worrier. He jokes about it himself, saying how his national executive won't get into the lift with him after a meeting on the top floor because they'll be clinically depressed by the time they get to the ground floor."

With an annual salary of €124,000, the 53-year-old father of three from Lusk, north Co Dublin has come a long way since his days working as a farm labourer and bin-man.

He left school at 15 and cut his union teeth as a young activist with the Agricultural Labourers' Union. Inspired by the thinking of Jim Larkin, whose worn mahogany chair sits in his office today, by 18 he was a shop steward and had organised his first strike. His working class heritage is the thing that still informs his thinking today.

After studying for the Leaving Certificate at night, he abandoned plans for further education to become more politically involved, flirting with an extreme left Trotskyite group in the 1970s. By the 1980s, he had joined the broader labour movement, and is a signed up member of the Labour Party today.

When SIPTU was formed in 1990, he was appointed regional secretary in the Midlands, his hard-line views on the protection of workers becoming more entrenched as the economy began to boom. When asked once what his hero James Connolly would have thought of the Celtic Tiger, he said "he would have been struck by the shallowness of it all. In the middle of this orgy of consumerism, we don't seem to be using resources to build a better society."

In 2003, O'Connor, who lives with his wife in a modest home on the outskirts of Naas, Co Kildare, took over from Des Geraghty as SIPTU president, and was re-elected unopposed in 2006.

The breakdown of the global financial system last year and what his old-school comrades call the 'collapse of capitalism' has left O'Connor feeling vindicated, and less inclined to hide his militant tendencies. In recent years, he has made high profile appearances at Sinn Fein and the Workers' Party Ard Fheiseanna.

Those who oppose him are familiar with his wrath.

"I've been on radio and TV programmes with him and every time I meet him, he makes it clear that he has a very serious personal distaste for me," says Jim Power, chief economist at Friends First.

"He fundamentally abhors everything I stand for. I always get the impression that he takes things very personally and can be quite abusive throwing out the old rhetoric about people like me being neo-liberals whatever that means.

"A lot of what I hear from Jack O'Connor is reminiscent of what I heard in the 70s and 80s. That model didn't work. If you look at the growth in wages and the history of industrial action during that period, it contributed to bringing the country to the brink of bankruptcy by 1986.

"We're back in that mode again with the same mantra. Jack's objective in life is to deliver for his members. He is one of the most powerful men in the country and if he delivers on that power, it will be a disaster for the economy and every man, woman and child in Ireland."

But John Carr, general secretary of the Irish National Teachers Union, claims his fellow trade unionist and friend is being wrongly demonised and misunderstood.

"Jack is one of the most genuine and sincere people I know in the trade union movement. He has such a strong sense of social justice and is just deeply concerned about people losing their jobs.

"Maybe he isn't as articulate as the top dogs that are put up against him but he is being vilified for standing up for the most vulnerable in our society."

Irish Independent