Some 2.5 million German workers now work a second job on the side - more than double the 1.2 million people who had two jobs in June 2003.
The number of people with a second job has increased significantly in the two years since the euro crisis began. The majority of them are women working tax-free 'mini-jobs' for €400 a month.
The development is "a clear indication that work no longer guarantees you have enough to live on, and the money from one job is not enough," Sabine Zimmermann, labour policy spokeswoman of the socialist Left party, told the Saarbrücker Zeitung.
But it's in Germany's richest regions where working on the side has become more popular. In wealthy Baden-Württemberg, 11.4 percent of employees had mini-jobs at the end of 2011, while in comparably poor Mecklenburg-Western Pomerania, it was 4.7 percent.
"The majority of workers with second jobs are well-qualified people with good incomes who earn something extra," Green Party labour expert Brigitte Pothmer told the paper.
She emphasized a different problem with the development: people who work overtime still pay insurance, taxes and social contributions based on those wages, unlike those who work mini-jobs, which are usually not taxed.
Pothmer said it was "extremely unfair to the insured population," and said the solution was to make mini-jobs less attractive by making it compulsive for those workers to pay social contributions.
But the government wants to do just the opposite, and plans to expand the mini-job programme and raise the tax-free earning limit to €450 a month, Der Spiegel magazine reported.