A senior leader of South Sudan's ruling party says its suspicions of foul play on the part of the North have been confirmed by a new report that finds discrepancies in the oil figures reported by Khartoum. Oil revenue sharing is a crucial component of the North-South peace agreement signed in 2005 and accounts for nearly all of the South's income.

The report released by resources and conflict research group Global Witness says that the oil numbers released by the North simply "do not add up."

The group says it found figures reported by the North do not match the figures reported by the oil companies operating in the South, potentially costing the Southern government significant portions of its annual oil revenue.

Pagan Amum (file photo)The secretary-general of the South's ruling Sudan People's Liberation Movement, Pagan Amum, told VOA the Southern government has been completely locked out by the North in all of the oil production processes within its territory.

"After four years of our sole, lonely voice, it has been confirmed that there has been serious discrepancies that might mean that the government of South Sudan has been cheated for hundreds of millions of dollars," he said. "We need transparency, and we are calling for transparency now."

Mr. Amum said that his party will raise the issue with the National Petroleum Commission to undergo a comprehensive review of the North's accounting methods as well as Khartoum's relationship with the oil companies.

But he said the international community may have to intervene.

"In the end of course we may need to resort to third-party international bodies to audit the petroleum revenue so that the Sudanese people really know how much of it has been used to their benefit," said the SPLM secretary-general.

The Global Witness report found that while the figures from northern oil fields, which are not subject to the oil sharing agreement, roughly matched those from the oil companies, the numbers from southern oil fields showed an under-reporting of oil production ranging from nine percent to 26 percent on the part of Khartoum.

The group notes that just a 10 percent fudge in the oil numbers would cost the Southern government $600 million a year, a sum great enough to cover the budget of multiple state ministries. The South gets 98 percent of its funds from the oil sharing revenue.

China receives five percent of its total oil supplies from Sudan, while the Japanese also import a significant share from the Horn of Africa nation. The group is calling for the two countries to apply pressure on Khartoum to institute transparent methods of dealing with its Southern counterparts.

The North and South are co-partners within a coalition national government set up by the 2005 peace deal.

The SPLM secretary-general said that the purposeful undercutting of the peace deal by the North is making the forced marriage between the two parties increasingly difficult.

"We have problems in the implementation because the National Congress Party is obstructing the full implementation of the , which causes tensions and difficulties in our relationship because this relationship is based on the peace agreement," he said.

Global Witness says inquiries made towards the Khartoum government on the accounting methods for the nation's oil production were left unanswered.