BBC News, Lagos
The conduct of Nigerian politicians and government institutions is marked by corruption and violence, says New York-based group Human Rights Watch.
Yar'Adua has promised to tackle corruption
In a report, it says their behaviour resembles criminal activity more than democratic governance.
Struggles for political office are waged violently by gangs of thugs recruited by politicians, it says.
But the group said Nigeria's new president has the opportunity and an obligation to take action.
Hundreds of Nigerians have lost their lives, while record high oil revenues have been lost to corruption or mismanagement.
Using the backdrop of April's general elections, the investigation by Human Rights Watch focused on Nigerian politicians' use of violence to win office, driven by the hope of looting state oil revenues and the culture of impunity that surrounds the whole system.
The problems are not new, but the concern is that they have become so entrenched, so widespread, that governance in this country has become mired in a state of crisis.
That's rather important given that one in five Africans live here, and most are mired in poverty, despite the country's huge oil revenues.
But the group says there is a window of opportunity.
Human Rights Watch has welcomed new President Umaru Yar'Adua's pledge to actually uphold the rule of law.
But it wants to see real reforms to make the government accountable and action to end the culture of impunity.
The report's author, Chris Albin-Lackey told the BBC that the problem is so deep and so widespread that reforms have to be faster and more dramatic than the new government has been willing to undertake to date.
Violence is commonplace during Nigerian elections
"And it has to mean holding some of the more notoriously corrupt and abusive figures of the past eight years to account for what they have done," he said.
Since Nigeria returned to civilian rule eight years ago, HRW says each election has been more violent and more rigged than the last.
The group says the governing party in Nigeria has helped entrench the system.
At every level, there are powerful interests at play.
The report highlights the role of local unelected kingmakers, known as godfathers, who use personal influence, money and violence to ensure their preferred candidates win office.
In return they get a slice of funds looted from state treasuries.
The consequences of this political system, in human lives, poverty and development are more than evident here, but reforming it, is no easy task.