The ends justify the means appear to be the basic political philosophy of fiercely ambitious Louisiana politician Willie Stark (Penn).

A charismatic demagogue, he rises from dirt-poor beginnings to champion the rights of the disadvantaged - mainly sharecropping blacks - at the expense on the oil firms and public utility companies that hold sway across the state.

Helping oil the wheels of his political bandwagon are Patricia Clarkson's manipulative press attaché and Jude Law's self-centred agent-come-fixer Jack Burden.

As Stark rises inexorably up the greasy pole to become governor, the rich and powerful who resent and fear his ascent plot to get him impeached.

Just to complicate matters Burden's surrogate father, the retired Judge Irwin (Hopkins), takes a principled stand against Stark, a position that could see him removed from office.

Writer-director Steve Zaillian's adaptation of Robert Penn Warren's 1946 Pulitzer Prize-winning novel focuses on its central themes of betrayal and idealism leaching into corruption.

Infusing it with classic noir elements, he has fashioned an atmospherically powerful piece but one that ultimately fails to convince.

The main problem is Penn's manic lead performance as a hectoring idealist - think Bono after a makeover by Ken Dodd's stylist - a display of overacting that distracts from other more subtle performances around him.

Law is fine if a little tepid as the observer through whom we see events unfold while the roles played by Kate Winslet and Mark Ruffalo are so underwritten they barely make a mark.

Despite the two-hour running time plot strands remain unexplored and the final reel is a rushed, unsatisfying climax to the slow-burning build-up that precedes it.

Tim Evans