Voters in Spain are heading to the polls for the second time in six months today after December's inconclusive parliamentary election failed to produce a government.

Opinion polls suggest the second vote will see a similarly fragmented result, despite growing public frustration over the political deadlock.

The big choice at the ballot box is between the outgoing conservative Popular Party and anti-austerity party Podemos.

Spain has only been ruled by single-party governments since returning to democracy in the 1970s.

December’s general election broke that mould, leaving the winning PP short of the number of seats needed to form a majority.

The Socialists (PSOE), who came second in the last poll, are tipped to slip into third place this time, behind Podemos.

The two left-wing parties could be in a position to form a viable government if the centre-right Ciudadanos, PP’s most natural coalition partner, fails to secure enough support.

Spain’s acting prime minister, Mariano Rajoy, urged the country to "convey a message of institutional and economic stability" after the UK voted to leave the EU on Thursday. 

Analysts have predicted that the referendum outcome may steer voters to traditional parties, including the PP, as mainstream politicians paint Podemos as a threat to the country's economy. 

Polls close at 7pm Irish time, with results expected before the end of the day.