Greece's leftist Prime Minister Alexis Tsipras accused Spain and Portugal on Saturday of leading a conservative conspiracy to topple his anti-austerity government, saying they feared their own radical forces before elections this year.

Tsipras also rejected criticism that Athens had staged a climb down to secure an extension of its financial lifeline from the euro zone, saying anger among German conservatives showed that his government had won concessions.

Greeks have directed much of their fury about years of austerity dictated by international creditors at Germany, the biggest contributor to their country's 240-billion-euro bailout.

But in a speech to his Syriza party, Tsipras turned on Madrid and Lisbon, accusing them of taking a hard line in negotiations which led to the euro zone extending the bailout program last week for only four months.

"We found opposing us an axis of powers ... led by the governments of Spain and Portugal which for obvious political reasons attempted to lead the entire negotiations to the brink," said Tsipras. “Their plan was and is to wear down, topple or bring our government to unconditional surrender before our work begins to bear fruit and before the Greek example affects other countries," he said, adding: "And mainly before the elections in Spain."

Spain's new anti-establishment Podemos movement has topped some opinion polls, making it a serious threat to the conservative People's Party of Prime Minister Mariano Rajoy in an election which must be held by the end of this year.

Portugal will also have elections after the summer but no anti-austerity force as potent as Syriza or Podemos has so far emerged there. Portugal’s Passos Coelho aligned himself with euro zone governments which have called for policies to promote economic growth but without trying to walk away from austerity as in Greece.