Greece’s top Supreme Court judge was named caretaker prime minister yesterday to lead the country to elections next month, ending a week of political deadlock after leftist leader Alexis Tsipras resigned.

Vassiliki Thanou, an anti-austerity advocate who has argued against wage cuts for judges and court officials, was sworn in as the country’s first female prime minister at 8pm. Her administration will take office today, when September 20 is expected to be set as the election date.

Her appointment ends a week of fruitless negotiations as top opposition party leaders took turns in attempting to form a government, exercising a constitutional right that takes effect if a prime minister resigns within a year of being elected.

The process dragged on for a week as the main conservative opposition and then the far-left Popular Unity party both used their allotted three days in full despite having no chance of success, hoping to delay the election. The conservatives said all must be done to avoid a new round of elections that Greece did not need.

Popular Unity leader Panagiotis Lafazanis – who broke his rebel far-left faction away from Tsipras’s Syriza party last week, taking a sixth of its lawmakers with him – used his three days to air his anti-bailout message before handing back the mandate yesterday.

Tsipras remains hugely popular in Greece despite making a U-turn to accept a bailout programme, and opposition parties feel a longer campaign period offers a better chance of denting his popularity as austerity cuts from the bailout start kicking in.

No major polls have been published in recent weeks but Syriza is expected to once again emerge as the biggest party in parliament when the snap election is held.

But Tsipras is not expected to secure an absolute majority, forcing him to find a coalition partner, failing which a second round of elections could be held.