Iraq dramatically increased the official size of its oil reserves yesterday after new data suggested that they could exceed Saudi Arabia’s and be the largest in the world.

The Iraqi Deputy Prime Minister told The Times that new exploration showed that his country has the world’s largest proven oil reserves, with as much as 350 billion barrels. The figure is triple the country’s present proven reserves and exceeds that of Saudi Arabia’s estimated 264 billion barrels of oil. Barham Salih said that the new estimate had been based on recent geological surveys and seismic data compiled by “reputable, international oil companies . . . This is a serious figure from credible sources.”

The Iraqi Government has yet to approve a national oil law that would allow foreign companies to invest. Mr Salih said that the delay was damaging Iraq’s ability to profit from oil output, robbing the country of potentially huge revenues. With oil selling for more than $125 dollars a barrel and demand rising, Mr Salih is frustrated that Iraq still struggles over the establishment of a regulatory framework. “There is a real debate in the Government and among political leaders about the type of oil management structures we should have. I am for liberalising this sector and allowing the private sector to come in to develop these vast resources.”

BP, Exxon Mobil, Chevron, Royal Dutch Shell and Total have been queuing for rights to exploit Iraqi reserves. Mr Salih confirmed that Iraq was negotiating the outlines of two-year deals with some of the companies. He was optimistic that a draft law could be approved in the near future.

“We need to recognise after so many decades of mismanagement of the oil industry that we need to call a spade a spade,” he told a group of delegates at the World Economic Forum in Sharm el-Sheikh. “We can regulate it, but we need private investment to develop Iraq’s production capacities.” He said that Iraq was pumping 2.5 million barrels of oil a day at present, earning about $70 billion (£35.9 billion) in revenue this year.

The price of oil bounced back to record highs yesterday when Opec refused to increase supplies following Saudi Arabia's promise to the US that it would provide an extra 300,000 barrels a day. In New York, the price of light, sweet crude for June delivery rose from $125.92 to US$126.35. In London, Brent crude for July delivery was up 82 cents at $125.81 per barrel.