Activist investment fund Nanes Balkany has built up a 5.1 per cent stake in Toreador Resources, an oil and gas exploration company, and is pushing the company to sell assets, pay debt and move its headquarters to Europe.

Toreador, which has stumbled recently over its attempts to sell its stake in a natural gas project in the Black Sea, is based in the US but has its key properties in France, Turkey, Romania and Hungary.