European anti-establishment parties of all political colours are rallying behind Greek Prime Minister Alexis Tsipras in his standoff with creditors, which threatens to force Athens out of the eurozone and undermine the single currency.

Parties with virtually nothing in common except a rejection of EU-imposed austerity are hoping public sympathy for Greece and its radical leftist leader will translate into a backlash against traditional parties and a boost in their own support.

Tsipras's battle has united parties as diverse as Spain's left-wing Podemos, the anti-immigrant Northern League and the grassroots 5-Star Movement in Italy, France's far-right National Front and the anti-EU United Kingdom Independence Party (UKIP).