* Spain, Portugal leading "axis of powers" against Athens-PM
* Portuguese leader denies taking hard line on Greece
* German anger shows Greece won concessions - Tsipras
* Spanish conservatives face serious threat from Podemos
By Costas Pitas and David Stamp
ATHENS, Feb 28 (Reuters) - 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 climbdown 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 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, who won an election on Jan. 25.
"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.
Rajoy went to Athens less than a fortnight before the Greek election to warn voters against believing the "impossible" promises of Syriza. His appeal fell on deaf ears and voters swept the previous conservative premier from power.
Portugal will also have elections after the summer but no anti-austerity force as potent as Syriza or Podemos has so far emerged there.
In an interview published before Tsipras made his speech, Prime Minister Pedro Passos Coelho denied that Portugal had taken a hard line in negotiations on the Greek deal at the Eurogroup of euro zone finance ministers.
"There may have been a political intention to create this idea, but it is not true," he told the Expresso weekly newspaper.
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.
"We were on the same side as the French government, with the Italian and Irish governments. I think it's bad to stigmatize southern European countries," he said.
A VICTORY FOR GREECE
Portugal had to take its own bailout in 2011 but left the program last year. Finance Minister Maria Luis Albuquerque said on Saturday Lisbon would start repaying its loans to the IMF next month, giving back 6 billion euros.
This contrasts to Greece which remains in its EU/IMF program, almost five years and two bailouts after it had to seek international help.
Tsipras has portrayed the Eurogroup deal as a victory for Greece, even though it meant extending the bailout program he had promised voters to scrap. He noted German lawmakers from Chancellor Angela Merkel's conservatives had attacked the Greek leadership when they approved the extension on Friday.
"We have all watched the strong opposition within Angela Merkel's party which shows that unacceptable concessions have been made to Greece," he said.
So far he has public backing. A poll conducted by the University of Macedonia for SKAI TV showed 56 percent of Greeks believed the extension had been a success, compared with 24 percent who said it represented a failure.
Ireland's finance minister has said Athens must negotiate a third bailout when the extension expires in June - something Tsipras denied on Friday.
Finance Minister Yanis Varoufakis called into question a major debt repayment Greece must make to the European Central Bank this summer, after acknowledging Athens faces problems in meeting its obligations to international creditors. (additional reporting by Andrei Khalip in Lisbon; Editing by Janet Lawrence)