Directed by Kenneth Lonergan Starring Anna Paquin, J Smith- Cameron, Jean Reno, Jeannie Berlin, Allison Janney, Matthew Broderick, Kieran Culkin, Mark Ruffalo, Matt Damon Club, IFI, 150 min

What might have ended up as a neat, well-acted monograph on the discontents of adolescence ultimately loses its way, writes DONALD CLARKE

IF YOU WEREN'T already aware of the kerfuffle surrounding the release of Kenneth Lonergan's rambling, baggy drama, you might be tipped off when the characters take a trip to the cinema. Among the movies playing are such 2005 releases as Serenityand Flight Plan. The world has ended several times since Margaret's wrap party.

Lonergan, director of You Can Count on Me,ended up in a murky squabble (punctuated by lawsuits) concerning the length of the final cut. When the current version, clocking in at a super-sized 150 minutes, finally reached US critics, many celebrated it as a misused masterpiece.

It's not quite that: too often the film's reach exceeds its grasp. But Margaret(named, somewhat pompously, for a Gerard Manley Hopkins poem) exhibits levels of grit and ambition that you rarely encounter in contemporary cinema.

Anna Paquin plays a pampered, precious Manhattan teen named Lisa Cohen. We see her cheating on her maths exam. We watch as, in half-bright, quasi-coherent fashion, she squabbles with classmates about responses to 9/11 (a whole half-decade more recent then, remember).

After a tad more fleshing out, the film finds Lisa joshing with a bus driver (Mark Ruffalo) as he approaches a busy street corner. Distracted, he breaks the red light and fatally injures a middle-aged woman (Allison Janney). An increasingly messy narrative spiral then spins out from this fulcrum. Should Lisa ruin the driver’s career by telling the truth? What responsibilities does she have towards the dead woman’s family?

While all these deliberations are taking place, Lonergan finds time to detail Lisa’s awkward advances towards a cool kid (Kieran Culkin) as well as her mother’s romance with a strange Colombian businessman (a notably French Jean Reno).

One unforeseen consequence of the delays surrounding the film's release is that, in Ireland at least, it emerges at much the same time as Stephen Daldry's unsatisfactory Extremely Loud and Incredibly Close. There are faintly eerie similarities between the projects. Both involve precocious, deeply annoying young people travelling through New York while they try to process a recent tragedy. Both protagonists snap ruthlessly at their unfortunate single mothers. Both films are concerned ( Margaretless explicitly) with the attacks of 9/11.

The Lonergan piece is, however, by far the more impressive work. Rather than resorting to sentimentality, the writer/director favours an ugly pseudo-realism that invests every scene with a slightly nauseous edge.

Paquin is to be congratulated for, with admirable lack of vanity, making an impressively irritating little squirt of Lisa. Even before she encounters her life-changing trauma, she is revealed to be manipulative and self-absorbed. Yet Paquin squeezes out enough vulnerability to confirm that she is still a victim of unsettled hormones.

The adults behave just as badly – mom (J Smith-Cameron) initially dismisses Lisa’s plan to change her testimony – but shield their compromises behind the fragile façade of maturity.

What we might have ended up with is a neat, well-acted monograph on the discontents of adolescence. Unfortunately, Lonergan has buried that pamphlet in a 19th-century epic of positively Russian proportions. Some of the subplots seem unnecessary. The copious shots of buildings, skylines and commuters feel like meretricious padding. The final half-hour descends into a class of hysteria that seems as inauthentic as it is hard on the ears.

Yet, this is one of those works – though the studio allegedly thought differently – whose flaws add to its undeniable appeal. One thinks of those vintage double albums that, though saddled with too many dud tracks, you wouldn’t wish a minute shorter.

Unlike the folk behind Extremely Loud, Lonergan fosters chaos rather than slipping into consoling neatness. Margaretdemands that viewers do their own filleting, but it ultimately proves worth the effort.