“Transparency and data is key to the smooth operation of markets," said the G-7 finance ministers after two days of talks ended in Britain on Saturday.

Bloomberg reports the ministers as saying their aim is to keep a lid on prices and open new sources of supply by ensuring “energy security" and “a climate conducive to investment”.

“We need more information about oil reserves," said UK Chancellor of the Exchequer Gordon Brown. "Transparency in the oil markets is now something that is necessary.”

Brown said he wanted industry groups and international financial institutions to draw up worldwide standards for reserves accounting. He also wanted producing nations to publish exact figures on supply.

The measures are designed to give traders better information on supply, replacing the estimates now made by consultants who track oil tankers, because producing nations such as Saudi Arabia withhold such data.

The proposals would also force companies such as BP Plc and the Royal Dutch Shell, Europe's two biggest oil companies, to publish data about their reserves on an internationally agreed basis.

Late last week Royal Dutch Shell said it was reducing its proven petroleum reserves by 1.4 billion barrels — substantially more than the 900 million barrels expected by analysts.

The fifth reserves downgrade in little more than a year overshadowed news that the group more than doubled its fourth-quarter net income to US$4.5 billion.