Nigeria's state oil firm NNPC Monday rejected as "misleading" a claim by auditors that it owed the government $8.3 billion (6.1 billion euros).
A report by Nigeria's oil industry watchdog covering the 2009-11 period "contains fundamental inaccuracies which are misleading, and (it) constitutes misinformation to the generality of the public," NNPC said.
The audit by the Nigerian Extractive Industries Transparency Initiative also found that the state oil firm consistently violated procedures in Nigeria's controversial fuel subsidy programme.
The Nigerian National Petroleum Corporation, itself a fuel importer, is required to follow the same procedures as private companies when submitting subsidy claims.
NNPC said that all such claims were duly verified and approved.
Nigerian President Goodluck Jonathan tried to scrap the graft-riddled subsidy programme last year, but the move sparked a wave of strikes and protests by those who saw the scheme as their only benefit from the nation's oil wealth because it keeps pump prices low.
The outcry forced him to partially reinstate the subsidy.
Mismanagement and allegations of corruption have long dogged the NNPC.
Jonathan sacked its managing director Austen Oniwon last June in a bid for "greater transparency and accountability in government," according to a statement issued at the time.