Greece’s beleaguered prime minister, Alexis Tsipras, has blamed the “absurd proposals” of creditors keeping the debt-stricken country afloat for the failure to reach a deal that could release emergency aid to avert default.

In a hard-hitting article for the French daily Le Monde, the leader lambasted the uncompromising approach of the EU, European Central Bank and International Monetary Fund for five months of fruitless negotiations.

“The lack of an agreement so far is not due to the supposed intransigent, uncompromising and incomprehensible Greek stance,” he wrote. “It is due to the insistence of certain institutional actors on submitting absurd proposals and displaying a total indifference to the recent democratic choice of the Greek people.”

The Greek leader held a telephone call on Sunday night with the German chancellor, Angela Merkel, and France’s François Hollande to discuss the situation. All three leaders reiterated the need for a quick agreement, according to one official in Athens.

Tsipras’s intervention via La Monde – on the day when his anti-austerity coalition had hoped to wrap up talks – came amid clear signs of strain in the Syriza-led government as senior members of the radical left party denounced the appointment of the Greek-American economist Elena Panaritis as Greece’s representative at the IMF.

By Sunday night some 43 Syriza cadres, including deputy prime minister Yannis Dragasakis, had signed a petition opposing finance minister Yanis Varoufakis’s choice of Panaritis. She had formerly represented the pro-bailout Pasok party as an honorary MP.

The row prompted Varoufakis to go on to Twitter on Sunday morning to deny that his position in Tsipras’s government could be at risk.

“Rumours of my impending resignation are (for the umpteenth time) grossly premature...”, he tweeted to his 425,000 followers.

Rumours of my impending resignation are (for the umpteenth time) grossly premature... — Yanis Varoufakis (@yanisvaroufakis) May 31, 2015

Varoufakis then told one follower that, as John Maynard Keynes put it, “in the long run we are all dead”, but “in the medium run, those nostalgic of the troika days are stuck with me”.

@nikimoza1 "In the long run we are all dead." J.M.Keynes. (In the medium run, those nostalgic of the troika days are stuck with me @ FinMin) — Yanis Varoufakis (@yanisvaroufakis) May 31, 2015

The furore came as senior eurozone officials insisted that both sides were still far apart in agreeing on the fundamentals of a cash-for-reform deal. Repeated expressions of optimism by the Greek government not only ran contrary to reality, but were aimed squarely at stopping a run on the banks, they believe.

“It is a lie that there is any optimism. There is no optimism. What the so-called optimism is about is stopping panic-stricken Greeks withdrawing deposits from banks,” said one well-placed source with access to high-level policymakers.

“Time is not operating in the interests of the Greeks, but the EU. The showdown is fast approaching and nothing can be ruled out. Very soon we may see staged capital controls.”

Officials from Greece have been locked in talks with creditors over the weekend in an attempt to agree a package of economic reforms. Outstanding issues include pensions, labour market reform, VAT rates and Greece’s budget targets. Europe’s main stock markets all fell late last week on fears that a deal will not be reached in time.

Sometimes I get the impression people are waiting for an accident so they can focus [on] avoiding a bigger disaster José Manuel Barroso, former EC president

On Friday, the economy minister George Stathakis announced that Athens had “the internal resources” to rustle up a €305m (£220m) payment to the IMF on 5 June, but stopped short of saying it could service debt obligations scheduled later in the month. In an interview with the Italian newspaper Corriere della Sera on Sunday, he said he expected a “a technical solution” to be clinched “in a few days”. Aid would then be unlocked at a meeting of eurozone finance ministers. Greece’s €240bn bailout programme expires on 30 June.

Indicative of the growing sense of foreboding, Australia issued an advisory at the weekend warning travellers of a potential breakdown in banking services. “Australians visiting Greece should be aware of the possibility that retail banking services … may at times become very limited at short notice,” the advisory said. “Protests and demonstrators can occur in cities across Greece with little warning.”

José Manuel Barroso, the former European commission president, warned on Sunday that it was vital to find a solution quickly. He told the BBC’s Andrew Marr show: “Sometimes I get the impression that people are waiting for an accident so that they can really focus [on] avoiding a bigger disaster. It’s too long, this time that has been taken to find a solution. I believe it’s important now to find that solution.”