French President Francois Hollande said Friday that Brexit cannot be "cancelled" or "delayed", after meeting with British Prime Minister David Cameron.

"The decision has been taken, it cannot be delayed and it cannot be cancelled, now they have to face the consequences," Hollande told reporters on the sidelines of Battle of the Somme centenary ceremonies in northern France.

"Being in the European Union has advantages," he said. "And that's... what the British are starting to understand. Those who were tempted by the Brexit are starting to think it over."

Hollande said a speedy Brexit "would avert all the uncertainties and instability, especially in the economic and financial domains. The faster it goes, the better it will be for them."