Thousands took to the street to demand that Golden Dawn is expelled from Greek parliament. Reuters

Protesters across Greece poured on to the streets of cities Friday night, denouncing the "dark force" of fascism as the spokesman of the neo-Nazi Golden Dawn party continued to elude arrest more than 24 hours after his extraordinary on-screen assault of two female leftwing politicians.

Nine days before fresh general elections, the fault lines in Greek society are deepening.

And late on Friday, as a police manhunt for Ilias Kasidiaris showed little sign of yielding a positive result, the divisions were on full display.

While anti-fascist demonstrators descended on public squares, supporters of Golden Dawn crammed into a hotel in Athens to hear the party's leader, Nikos Michaloliakos, rail against immigrant "scum" and the corrupt and crooked system that had brought the crisis-hit country to such a "dark place".

"There is growing polarisation. People are becoming increasingly radicalised thanks to all the rhetoric in the EU and here against the anti-austerity leftist majority and that is opening the door for Golden Dawn," said veteran activist Petros Constantinou. "We are demonstrating not only against the rise of the far right but against those who have enabled fascism to take root."

Constantinou, a tall, thin man who has spent years running an organisation that protects migrants, is, like a growing number of Greeks, convinced that it is the police who have facilitated Golden Dawn. "Without police cover and protection Golden Dawn would not have survived," he said. "And the proof of that is the failure to capture Kasidiaris.

"How is it possible that a man can do what he did in a television studio and yet manage to get away and stay on the run after a state prosecutor has ordered his arrest? The police clearly don't want to arrest him."

Dimitris Trimis, the head of the Greek journalists' association, ESEA, agreed. In a nation where physical violence is rare – and public displays of violence against women even rarer – Kasidiaris's assault on Liana Kanelli and Rena Dourou, during a live TV debate of politicians representing the seven parties that won seats in the country's inconclusive 6 May election, had clearly shocked Greeks.

All day Friday, TV channels had replayed footage showing Kasidiaris, a former commando in the Greek army, lashing out at Dourou first, hurling a glass of water in her face before turning his fists on Kanelli, the KKE communist party's spokeswoman, a former news anchor.

But his ability to evade arrest was entirely plausible, said Trimis.

"Suspicions of the collaboration between the police and Golden Dawn were confirmed at the ballot box in May," he said.

"As much as 50% of the police force voted for the party. There might be all the political will to arrest Kasidiarias. But there is a certain level of unwillingness among the police force that will stop that happening."

For years, he said, rightwing extremists had done the police force's "dirty work", mopping up migrants from the ghettoes of inner Athens in exchange for protection.

The spokesman of the Hellenic police force, Thanassis Kokkalakis, denied the accusations and said special units all over Greece were looking for Kasidiaris.

"Our belief is that he is hiding in the knowledge that the arrest warrant runs out at one minute past midnight. He doesn't want the media all over him, showing him in handcuffs ahead of the election."

Golden Dawn is widely regarded as Europe's most fanatical neo-Nazi party, going so far as to ensure that its emblem bears an uncanny resemblance to the swastika.

By playing on deep disgruntlement over the punishing income cuts and tax increases demanded by creditors in return for rescue loans, it won 7% of the vote last month – ushering the hard right's entry into parliament for the first time since the collapse of military rule in 1974. Although polls have shown its popularity dropping to as low as 3.6% as Greeks gear up for a second election, it would be enough to allow the party representation in Athens' 300-seat house.

Emboldened by the growing divisions between left and right, rich and poor, Golden Dawn has resolutely refused to condemn or even reprimand Kasidiaris for his behaviour. A party statement said the spokesman had instead been provoked by the female politicians.

"Ms Kanelli got up first ... hitting him unprovoked in the face with a sheaf of documents," it said.

The denial fits in with the neo-Nazi party's history of terrorising women, including female journalists whose photographs and passport numbers have been published in the party's weekly newspaper.

With Thursday's assault quickly followed by Golden Dawn attacks on socialist MPs campaigning in northern Greece and leftwing students at Athens' Panteion University, there are mounting concerns that the darkening mood could be a precursor of worse to come – even if Kasidiaris's explosive temper has shone a spotlight on the party as never before.

On television and radio chatshows commentators voiced fears that in a country where memories of the brutal 1946-49 civil war are still vivid, Greece could be hurtling towards a full-scale social breakdown – sparked initially by its worst economic crisis in modern times and now exacerbated by the political uncertainty engulfing the nation.

"After months of extreme hate speech, violence has climaxed," wrote the analyst Vivian Ethymiopoulou in the mass-selling Ta Nea newspaper.

"From verbal run-ins and yoghurt throwing we have officially passed to acts of personal revenge and daggers being drawn."