President Muhammadu Buhari will meet the head of a leading global watchdog on corruption to see how billions of dollars in oil revenue leakage can be curbed.

The head of Oslo-based the Extractive Industries Transparency Initiative (EITI) is expected to meet Nigeria’s president or vice president this week, its local arm said on Monday.

Stamping out corruption was one of the main pledges of Buhari’s campaign.

The Head of EITI, Clare Short has come to see how its recommendations can be implemented and help with long-term reforms. The initiative sets global standards for openness in the natural resources industries.

The Executive Secretary of EITI’s Nigerian arm (NEITI), Zainab Ahmed said last week that over $7.5 billion between 1999-2011 still needed to be recovered from oil and gas companies in Nigeria.

“The amount represents clear cases of underpayments, under-assessments of taxes, royalties, rents...which have not been adequately addressed in the past,” she said.

NEITI has suggested selling the state oil company’s stakes in producing joint ventures to fix its budget woes, a call echoed by many in the new administration, as well as scrapping the expensive and graft-riddled fuel subsidy.

The government relies on oil sales for the bulk of its revenues but there has been little oversight of how these are handled.

Former Central Bank Governor Lamido Sanusi was sacked under former President Goodluck Jonathan after he had said that up to $20 billion in oil revenues between 2012 and 2013 had not been remitted to the government by the state oil company NNPC. Buhari said he would re-examine this allegation.

Ahmed also said NEITI audits showed that some $11.6 billion of dividends between 1999 and 2012 from the government's investment in the Nigerian Liquefied Natural Gas (NLNG) company were not remitted by the state oil company.

“NNPC was unable to provide any evidence that the funds were remitted to the federation as required by law,” she said.

NNPC said the issue of reconciling accounts had been raised at a previous Inter-Ministerial Task Team and would be discussed at one this week. The team was designed to implement NEITI’s findings.

NEITI has also said the sale of eight oilfields to NNPC's upstream arm in 2010-2011 should be reviewed, as they were sold at $1.85 billion of which only $100 million was remitted to the federation account in February 2014.

Before he was sacked, Sanusi also criticised some of these deals for being awarded non-competitively to companies that supplied no services.

•Adapted from a Reuters report. Photo shows President Buhari.