Last month, the government agreed to pay fishermen a higher diesel subsidy after they blocked Mediterranean ports. And truck drivers called off a two-day strike in October after the government agreed to let regional authorities exempt them from a fuel tax used to finance health care.

Now farmers are threatening to block roads across Spain next week if the government refuses to ease tax on fuel.

Caruana, a member of the European Central Bank's Governing Council, said fuel tax cuts or higher subsidies aimed at softening the impact of higher energy prices on sectors such as transport or fishing "can have counter-productive effects."

"Although this kind of measure can help to cover the possible losses generated in the short term, they do so at the cost of delaying and obstructing the introduction of changes in productive processes that promote greater energy efficiency or the use of alternative energies, which are the correct response in the long term," he told a Spanish Senate committee.