John Monks, former head of the TUC, said he had been ‘shocked’ by the severity of the warning from Mr Barroso, who is a former prime minister of Portugal.

Mr Monks, now head of the European TUC, said: ‘I had a discussion with Barroso last Friday about what can be done for Greece, Spain, Portugal and the rest and his message was blunt: “Look, if they do not carry out these austerity packages, these countries could virtually disappear in the way that we know them as democracies. They’ve got no choice, this is it.”

‘He’s very, very worried. He shocked us with an apocalyptic vision of democracies in Europe collapsing because of the state of indebtedness.’