Russia’s slumping oil production is, in part, due to the increasing pressure on Exxon-Mobil’s Sakhalin-1 oil and gas venture as the state tightens control over the energy sector, according to William Ramsay, deputy head of the International Energy Agency.

Mr Ramsay, who is visiting Moscow this week for talks with government officials, said the drop in output in Russia in the first three months of this year was largely due to uncertainty over the investment climate.