As part of the BBC's Energy Week, we are looking at who controls the bulk of the world's oil and gas reserves.

We often think of Big Oil, and big energy, as a crowd of huge multi-national companies whose motives are pure commercial self-interest. But the truth is a large majority of the world's fuel reserves, and that includes 90 per cent of its oil, are under the control of national governments.

Many argue there's a growing politicisation of energy. Take Russia's enormous potential influence on states which depend on it for natural gas supplies. The European Union it seems, and especially France, is worried that Russia wants to control the whole energy chain and use gas as a geopolitical tool.

Only this week, the Saudi leadership expressed upset that US President George Bush had talked about massively reducing America's dependence on Middle East oil. And increasingly, states have deep pockets to buy new reserves.

Should we be worried that governments are so much in control of the world's fossil fuel supplies?

Joining Lesley Curwen to discuss this are from Oslo, Dr Fatih Birol, chief economist of the International Energy Agency, representing 26 governments from the developed world, also from Norway, in Stavanger, Tor Kartevold, special adviser on oil market issues for Norway's state-owned oil company Statoil, and from Boston, Mike Lynch, a consultant and former academic, now at Strategic Energy & Economic Consulting.