In an atmosphere that has become increasingly electric before Greece's crucial election, the far-right Golden Dawn has ratcheted up the rhetoric by threatening to remove immigrants and their children from hospitals and kindergartens.

Earning loud applause at an election campaign rally in Athens, Golden Dawn MP Ilias Panagiotaros said: "If Chrysi Avgi [Golden Dawn] gets into parliament [as polls predict], it will carry out raids on hospitals and kindergartens and it will throw immigrants and their children out on the street so that Greeks can take their place."

Medical supplies and beds at some hospitals are running desperately short. The governor of the state-run Nikea hospital, Theodoros Roupas, called on doctors to stop non-essential surgical interventions because of a critical shortage of gloves, syringes and gauze. The order was revoked when Roupas found emergency supplies later in the day.

"The situation is really critical and getting worse every day," said Dr Panaghiotis Papanikolaou, a neurosurgeon at the hospital. "There is not enough medical staff to cope and huge shortages of supplies. There's no money to even service scanners and surgical microscopes … we're talking about a major healthcare crisis – not in the making, it is happening now."

The paralysis spawned by six weeks of political instability following Greece's indecisive poll on 6 May has exacerbated the country's parlous public finances. Sunday's fresh general election is viewed as decisive for the county's future in the euro.

Alexis Tsipras, leader of the leftwing Syriza alliance, said it was obvious that Greece's rudderless state could no longer continue. A government had to be formed. "The country has to have a government, be it of the right or left," he said. Syriza is neck and neck with the conservative New Democracy party.

"The next 10 days following the election are extremely important," he said referring to a host of critical EU meetings, including an emergency summit scheduled at the end of the month.

He said the forthcoming vote would boil down to a single choice – whether Greeks wanted to support or reject the "memorandum" of onerous terms demanded by the EU and IMF in return for financial assistance.

"Greeks should know that, if Syriza is elected, there will be no memorandum on Monday," he said. "Syriza will replace the memorandum with a national plan of recovery … I think we have been totally clear." He said Syriza would ensure that minimum wages were increased, unemployment benefits extended and the public sector expanded.

Tsipras and his colleagues attempted to brush off the shock defection of Nikos Hanias, Syriza's candidate in Corinth. In an excoriating letter, the veteran leftist lambasted the party, saying its elevation to power "if only for an hour" would be catastrophic "for Greece and our children".

"It is shameful and dishonourable that, by exploiting the justified rage of society, you are gambling with our future, betting on the non-existent possibility that our creditors are bluffing without proposing something if the case is the contrary," Hanias wrote. He said he could no longer participate in a party that was "extremely dangerous for the Greek people and its future".

Conceding that Syriza was a conglomeration of parties "with many tendencies," Tsipras suggested the extraordinary outburst was linked to campaign dirty tricks. Hanias, who failed to be elected in last month's inconclusive election, had previously been a member of the socialist Pasok before joining the leftwing coalition.

"I want to say that we are ready for everything, and to see everything. When a system of power sees the ground slipping from underneath it, it can do anything," said Tsipras.