Pablo Iglesias, whose party won a surprisingly high 69 seats in a parliamentary election on December 20th, refused to talk of forming alliances after meeting with acting Prime Minister Mariano Rajoy.
Instead he said the priority for Podemos when parliament reconvenes on January 13th will be to help the poor by proposing a "social emergency" law that prevents families from being evicted for not paying their mortgage or ensures pensioners can buy their medicine.
"There are Spaniards who cannot wait," Iglesias, whose cheap supermarket clothing contrasts sharply with the suits of other party leaders, told a news conference after his talks with Rajoy.
Rajoy's conservative Popular Party won the most votes in the election but lost is absolute majority, taking 123 seats in the 350-seat lower house of parliament - down from the 186 it got in 2011.
He is trying to form a minority government but is struggling to get support from other parties.
Podemos, which came in third place in the election despite having been founded just two years ago, and the Socialists, which came in second with 90 seats, refuse to support Rajoy.
The leader of the Socialists, Pedro Sanchez, wants to form a left-wing government with Podemos.
But Sanchez on Monday demanded that Podemos abandon its support for an independence referendum in the wealthy northeastern region of Catalonia.
The vast majority of Catalans support holding such a referendum, which all national parties except for Podemos oppose.
Sanchez said on Monday that the "prior condition" for talks with Podemos is that it "renounce any position that implies the rupture of the coexistence between Spaniards".
Iglesias, a fan of the TV series "Game of Thrones" who has described politics as "the art of accumulating power", refused.
"The only way to defend the unity of our country is through democratic processes," he said.
Podemos wants Catalonia to remain a part of Spain and appears to bet that Catalans will reject independence in a referendum like Scotland did last year and Quebec did in 1980 and 1995.
Iglesias accused the Socialists of being more preoccupied with internal power struggles than with the interests of voters.
He also defended his proposal to have an independent left-wing friendly personality be appointed prime minister instead of Sanchez, whose leadership of the Socialists in contested by top party members.
"It is a possibility called for in the constitution... it could serve to overcome the deficiencies of a candidate who does not appear to have the support of his own party," Iglesias said.
Rajoy also met with the leader of new centre-right party Ciudadanos, which came fourth in the election winning 40 seats.
Albert Rivera presented Rajoy with all the reforms which his party wants to pass with the support of the Popular Party and the Socialists.
If there is still a deadlock after two months from a first vote of confidence in parliament on a new prime minister, new elections must be held.
By Patrick Rahir / AFP