Reintroducing permanent border controls in Europe's passport free travel area to respond to the refugee emergency could cost France more than a billion euros a year and perhaps 10 times that longer-term.

A French government-sanctioned think tank said Wednesday that half would come from a loss of tourists discouraged by having to apply for multiple visas.

France Strategie said direct costs to the French economy would run to 1-2 billion euros ($1.1-2.2 billion) each year depending on how frequent border controls are.

This includes the impact on cross-border workers and freight transport costs but does not take into account the extra expense France would face to carry out ID and other checks.

Longer-term, the controls could slow trade by up to 20 percent, costing more than 10 billion euros.