Support for Spain's socialist party has grown sharply in recent months alongside a rise in popularity for the far-right, a poll of polls ahead of next month's snap election shows.

According to the El Pais calculation, Prime Minister Pedro Sanchez's left-wing party is on course to win 27.3 per cent of the vote, giving the socialists a projected 113 seats.

But with little more than six weeks to go, the poll of polls showed the far-right Vox party also gaining sharply with a 12.1 per cent vote share.

Vox currently holds no seats in the Spanish parliament and an outcome similar to the poll projection would be regarded as a significant victory for the party, which stands on an anti-immigrant platform.

The snap election was called in February after Mr Sanchez’s budget was voted down.

Protests as Catalan leaders face trial: in pictures Show all 13 1 /13 Protests as Catalan leaders face trial: in pictures Protests as Catalan leaders face trial: in pictures Pro-union protesters demonstrate outside the Supreme Court in Madrid Reuters Protests as Catalan leaders face trial: in pictures A separatist protester holds a sign reading "When injustice becomes law, rebellion is a must" outside the Supreme Court in Madrid AFP/Getty Protests as Catalan leaders face trial: in pictures Separatist protesters hold a banner reading "Nationalism is supremacy" outside the Supreme Court in Madrid EPA Protests as Catalan leaders face trial: in pictures A protester holds a Catalan pro-independence Estelada flag during a protest outside the Supreme Court in Madrid AFP/Getty Protests as Catalan leaders face trial: in pictures A separatist protester holds up a banner during a protest outside the Supreme Court in Madrid Reuters Protests as Catalan leaders face trial: in pictures Basque people hold a sign reading "you will never walk alone, we are with you. Basque Country is always with Catalonia" outside the Supreme Court in Madrid AFP/Getty Protests as Catalan leaders face trial: in pictures Protesters hold banners mocking the trial of jailed Catalan separatists outside the Supreme Court in Madrid AFP/Getty Protests as Catalan leaders face trial: in pictures Separatist protesters hold up signs and banners during a protest outside the Supreme Court in Madrid Reuters Protests as Catalan leaders face trial: in pictures Separatist protesters hold Catalan and Spanish Republican flags and a banner reading "deciding is not a crime" outside the Supreme Court in Madrid Reuters Protests as Catalan leaders face trial: in pictures Pro-union demonstrators hold a sign depicting former President of the Catalan Government Carles Puigdemont reading "Puigdemont not ours" outside the Supreme Court in Madrid Reuters Protests as Catalan leaders face trial: in pictures Pro-union demonstrators hold Spanish flags with the message "hooray for the unity of Spain" outside the Supreme Court in Madrid EPA Protests as Catalan leaders face trial: in pictures Catalan regional president Quim Torra (C-R) and Catalan regional parliament speaker Roger Torrent (C-L) take part in a protest against the trial of jailed Catalan separatists in Madrid AFP/Getty Protests as Catalan leaders face trial: in pictures The president of Catalonian Parliament, Roger Torrent, center, and the Catalan regional President Quim Torra walk with protesters holding a banner that reads "to choose is not a crime" outside the Supreme Court in Madrid AP

The vote, the third in under four years, is a further sign of an increasingly fragmented political scene, with Catalonia‘s independence push dominating recent debate.

Mr Sanchez took office after ousting his predecessor, Mariano Rajoy, in June last year, when he won a no-confidence vote triggered by a damaging corruption conviction affecting the main conservative opposition People’s Party (PP).

But the simple majority of Socialists, anti-austerity and regional nationalist parties that united at the time against Mr Rajoy crumbled in February after Mr Sanchez refused to accept talks over Catalonia’s self-determination as part of the ongoing dialogue with separatists.

To win an outright parliamentary majority on 28 April, any one party needs to secure at least 176 seats.

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The projection – taken as an average of dozens opinion polls - shows the socialists and the far-left platform Podemos (on 13.8 per cent, or 36 seats) together would reach 149 seats – 27 seats short and leaving them to rely on the support of smaller, regional parties to form a majority government.

The PP saw its support drop to 20 per cent, or roughly 75 seats, in the polls.

And with the centre-right Ciudadanos also falling to 16.3 per cent, or 58 seats, even a coalition of the three right-wing parties would fall short of a majority in parliament.