The German government has estimated for the first time that debt relief measures for Greece, agreed by EU finance ministers last month, will cost around €34 billion ($39.8 billion) over the next decade, the Frankfurter Allgemeine Zeitung (FAZ) daily reported on Wednesday.

FAZ cited a document from the finance ministry as saying that the figure quoted depended on interest rate conditions.

"The volume of additional interest rate deferments over 10 years depends on actual interest rate conditions and is currently estimated by the federal finance ministry to be around €34 billion," the ministry said in a written response to a parliamentary question.

The ministry added that any deferred interest payments would have to be repaid by the Athens government after 2033.

Read more: EU bailout decision unlikely to soothe Athens' Sisyphean headache

FAZ said deferment of interest would lead to a reduction of up to €230 million a year in the revenues of the EU's European Financial Stability Facility, a fund set up to tackle the euro debt crisis. The waiver of profits from bonds held by other central banks would amount to €417 million in the 2018 German federal budget alone.

In June, Eurozone finance ministers and the International Monetary Fund (IMF) extended maturities and deferred interest payments on €96 billion worth of Greek debt — about one third of the country's overall debt pile.

Loan deferral plan

The deal included further loan extensions, taking the average loan term to 42.5 years, while allowing the deferral of interest and repayments for up to 15 years.

Greece has the highest debt-to-GDP ratio in the euro zone, at almost 180 percent of its national output.

Last month's deal has been denounced by Germany's business friendly Free Democrats (FDP) and the far-right Alternative for Germany (AfD) as effectively another write-off of Greece's debt.

Read more: Despite the data, little relief felt by ordinary Greeks

FAZ cited the respected economist, Friedrich Heinemann of the Centre for European Economic Research, who backed up their criticism.

Heinemann said the continual extension of maturities and deferrals of interest rates was basically "a delay in bankruptcy," adding that most of the loans would have to be written off.

"The idea that the latest rescue deal won't cost Germany or the other lenders and guarantors money is economically absurd. The nominal value of the receivables from Greece is purely a paper promise; they are in no way recoverable," said Heinemann.