Impose six-day working week or risk losing bail-out, Troika warns Greece

It adds that the government should also reduce daily rest between shifts to the 11 hours minimum and scrap restrictions on the length of shifts.

However, Greek employers will still be bound by EU labour laws such as the directive on working time, which requires workers to average no more than 48 hours per week over a four month period.

The leaked letter, which was circulated to Greek government departments last week, is the latest indication from the stricken country's creditors that there will be no further relaxation of the terms governing Greece's €300 billion bail-out.

Prime Minister Antonis Samaras has also been told to find an additional €11.6 billion of cuts for 2013 and 2014 despite the publication on Tuesday (4 September) of a report by the Center of Planning and Economic Research (Kepe), a Greek economic research body, maintaining that the new cuts would deepen the country's five year recession by a further 4 percent.

Despite this, Troika officials and EU politicians have continued to accuse the Greek government of dragging its feet in implementing labour market reforms.

On Tuesday (4 September) German Finance Minister Wolfgang Schauble insisted that there was no further wriggle-room at a meeting with Greek counterpart Yannis Stournaras in Berlin. In a statement on the German finance ministry's website, Schauble stated that it was "vital that Greece fulfils its promises completely."

Later this month the Troika is expected to present its report on the pace of Greek reforms to determine whether to continue the rescue package.

The next €31 billion instalment is dependent on a favourable assessment.

Recent data collected by Paris based think-tank the OECD found that Greeks worked 2,109 hours per year, more than 20 percent higher than the eurozone average of 1,573.

However, with the country's unemployment rate now the second highest in the eurozone at 23 percent, including an eye-watering 55 percent of under 25s out of education, training or work, Greece lags behind in total hours worked.

The Troika argues that weekend working hours could help boost competitiveness in the labour market.

Samaras' coalition government is also facing down continued public protests against the severity of the cuts.

On Tuesday, 300 pensioners stormed the health ministry demanding a meeting with minister Andreas Lykourentzos over new healthcare cuts. As with previous budget cuts, further cuts to public spending would be dependent on adoption by the Greek parliament.