UKIP Leader Nigel Farage said: "Far from being a cause of peace, the European Union has increased hostility in Europe.
"Ultimately it is a lack of democracy that leads to war and conflict. The EU's crushing of democracy in Greece has led to the rise of extreme parties such as Golden Dawn.
"Does Mr. Cameron really think the violent clashes in Athens last night represent peace?
"The anti-democratic EU, far from bringing countries together, has divided Europe. As they continue to drive through the failed Euro single currency project, it is the lives of ordinary citizens across Europe who suffer at the hands of the EU nationalists who refuse to contemplate anything than deeper, total and complete EU integration.
"If we Remain in the EU we will be locked inside a failed project that is pushing towards closer fiscal, political and military union, no matter the pain and suffering it brings to the people of Europe."