European farmers have threatened to blockade supermarket deliveries and leave shelves bare as part of their biggest tractor protests against the EU yet.

They are furious after Ursula von der Leyen, the European Commission president, announced a free trade agreement with the Mercosur trading bloc of South American countries.

The deal, which farmers fear will leave the EU swamped with cheap beef and poultry, requires the sign-off of bitterly divided European governments which could veto it.

Negotiations had dragged on for 25 years before Mrs von der Leyen swooped to sign the deal when France, the most influential member state opposing the deal, was engulfed in a domestic political crisis.

Yet it remains  a huge risk for the EU chief, who has staked her credibility on the controversial agreement in the first days of her second five-year term, which began on Dec 1.