Alexis Tsipras. Greek prime minister, addressing the nation, July 01, 2015

Greece will require at least €60bn in new financial aid over the next three years and debt relief to give it a chance at sustainability, the International Monetary Fund warned on Thursday.

The IMF said in a report that Europe should grant the country “comprehensive” debt relief, calling for the doubling of the maturities on its debts from 20 to 40 years.

The report says: "There is a substantial weakening in the delivery of structural reforms and in the reform commitments. This has made untenable the assumption until the last review that Greece would go from having the lowest average TFP growth in the euro area since it joined the EU in 1981 to having among the highest TFP (total factor productivity growth), and that it would go to the highest labor force participation rates and to German employment rates . Thus, relative to the last review, staff has downgraded the real long-term growth rate by 50 basis points to 1½%. (Growth in the 2- 3% range is assumed over the next few years, as confidence returns and the output gap is gradually closed.) Clearly, growth risks remain to the downside, which is examined in the robustness scenarios...to ensure debt can be deemed sustainable with high probability."

The Financial Times reports that with the expiry of the Eurozone’s bailout on Tuesday this week, Greece would need a further €10bn for the next four months, a senior IMF official said on Thursday. Moreover, there was a very real possibility that they would rise further as a result of the deteriorating economic situation.

“Clearly this is subject to very significant downside risks now,” a senior IMF official said. “It is urgent that we get out of this current situation.”

Leading EU officials have cast Sunday's Greek referendum vote as being on the future membership of the euro but the Greek government which is calling for a No vote says it is on strengthening its hand on negotiating with the bailout institutions.

In a television interview broadcast Thursday night, Alexis Tsipras, Greek prime minister, said voters should reject the creditors’ demands and he stressed that the country would have a bailout deal within 48 hours after the vote if they did.

“If ‘no’ wins, I can assure you that the next day I will be in Brussels and there will be a deal,” he said.

Jeroen Dijsselbloem, the Dutch finance minister who is president of the Eurogroup of Eurozone finance ministers, said a “No” vote wouldn’t entail Greece automatically leaving the common currency. But he stressed it would be an illusion for voters to believe that by voting “no,” Greece would be in a position to negotiate a better bailout package.

The FT says that the governing council of the European Central Bank is "set to reconvene on Monday and will almost certainly toughen the terms of emergency loans to Greece’s largest lenders if Greeks vote no in Sunday’s referendum, officials said. That could push one or more of the country’s biggest lenders over the edge and hasten Greece’s exit from the currency union."