Madrid: The heads of some of the world's biggest oil companies countered on Monday Opec claims that speculators were driving high oil prices, blaming instead a dearth of new supplies.

The chief executives of Royal Dutch Shell Plc, BP Plc and Spain's Repsol YPF said that restrictions on where they can invest and high taxes meant they could not help boost supplies as much as they might.

BP's CEO Tony Hayward said the argument that financial investors buying oil futures were behind a four-year rally that pushed oil prices to new records above $143 per barrel on Monday was a "myth".

He said the problem was a failure of supply growth to match demand growth. "Supply is not responding adequately to rising demand," he told thousands of delegates at the World Petroleum Congress.

Repsol CEO Antonio Brufau agreed. "The fundamentals in the industry are the significant reasons for having these prices," he said.

Shell Chief Executive Jeroen van der Veer said there was enough supply to meet current demand but that the market was tight and that many users were justifiably worried that future supplies will not meet demand.

Insofar as financial investors were involved in the market, they were only following such supply fears.

"We don't think that the financial markets are leading the speculation, probably they follow what other people fear as long term fundamentals," Van der Veer said. "I do not think that you can blame speculation for the oil price".

Van der Veer said while the world's third-largest oil company by market value did use energy derivatives it did not speculate on the oil price and that its net trading position was balanced.