The report, seen by the BBC, was commissioned by the oil minister in the wake of this year’s fuel protests to probe the financial side of the sector.
It says $29bn (£18bn) was lost in the last decade in an apparent price-fixing scam involving the sale of natural gas.
It also calculated the treasury loses $6bn a year because of oil theft.
Nigeria is one of the world’s biggest oil producers but most of its people remain mired in poverty.
Missing billions revealed this year
$400bn – estimated amount of Nigeria’s oil revenue stolen or misspent since independence in 1960 – World Bank’s ex-vice-president for Africa, Oby Ezekwesili said in August
$6.8bn – the amount a fuel subsidy scam has cost Nigeria over the last two years – a parliamentary report said in April
$29bn – the amount lost by the treasury in the last decade in an apparent gas price-fixing scam – leaked Petroleum Revenue Special Task Force report in Octoberr
$6bn – the amount the treasury loses a year because of oil theft – leaked Petroleum Revenue Special Task Force report in October
Nigeria’s president ‘must act over fuel scam’
Will Africa ever benefit from its natural resources?
The Petroleum Revenue Special Task Force report is one of several commissioned by the government – and follows an outcry after a parliamentary investigation uncovered a massive multi-billion fuel subsidy scam.
That had been set up after angry nationwide protests in January when the government tried to remove a fuel subsidy.
Earlier this week, a campaign was launched to clean up Nigeria’s oil sector.
It was led by Patrick Dele Cole, a politician from the oil-rich Niger Delta region, who said that 90% of the stolen oil was refined in eastern Europe and Singapore.
The BBC’s Will Ross in Lagos says this leaked report exposes the extent of the rot in Nigeria’s oil and gas industry – all the way from the awarding of contracts to the sale of refined