Peter Voser, chief executive of Royal Dutch Shell, and Christophe de Margerie, his counterpart at France’s Total, used the Oil & Money conference in London on Tuesday to highlight the potential energy windfall if sanctions preventing international oil companies from dealing with Tehran were lifted.

“Longer term, Iran’s oil and gas resources will have to be developed to meet demand,” Mr Voser said.

He was echoed by Mr de Margerie, who said that he hoped doing business with Iran would again be permitted “as soon as possible, not just for Total but for the world and for Iran. Any country cannot stay out of the system.”

Before the tightening of sanctions against Iran a few years ago, Shell and Total were two of the most active companies doing business with the Islamic republic.

In 1999, Shell defied a US sanctions threat to sign an estimated $800m (£492m) deal with Iran to develop two offshore oil fields in the Persian Gulf known as Soroosh and Nowrooz.

The project was completed in 2005. Until 2009, Total was involved in the drawn-out development of Iran’s vast South Pars natural gas field, also in the Gulf’s waters.

Iran has said it would be willing to offer access to its controversial nuclear programme if the US lifted its economic sanctions. A recent call between US president Barack Obama and his Iranian counterpart Hassan Rouhani — the first such dialogue between the two nations for more than 30 years — has raised hopes that a diplomatic solution can be found which could eventually mean Iran is again accessible to international oil companies.

Shell was reportedly blocked earlier this year from settling a $2.3bn debt with Iran through the supply of grain and medicine.

Since an oil embargo was imposed in July, the European Union has extended sanctions to include gas exports and shipbuilding equipment.