The Organisation for Economic Cooperation and Development has again cut its growth forecasts for the eurozone, and is calling on the European Central Bank to consider doing more to boost growth.
The organisation says the eurozone will shrink by 0.6% this year, widening the gap between it and faster-growing economies such as the US and Japan.
The UK forecast was revised down to 0.8% growth this year and 1.5% in 2014, the BBC reports.
In its twice-yearly Economic Outlook, the OECD said prolonged economic weakness in Europe could damage the global economy.
The organisation, which represents 34 advanced economies, forecast average growth across its members of 1.2% this year and 2.3% in 2014.
It said eurozone unemployment would continue to rise from its current rate of 12%, stabilising in 2014.
Meanwhile, the European Commission has given France two more years to complete its austerity programme.
France fell back into recession in the first three months of the year. Spain, Poland, Portugal, the Netherlands and Slovenia have also been given more time to complete fiscal tightening.
The move suggests a shift away from a focus on austerity in Europe, the BBC says.