A decree issued last week by the country's bishops cast a spotlight on the longstanding practice in Germany and a handful of other European countries in which governments tax registered believers and then hand over the money to the religious institutions.

In Germany, the surcharge for Catholics, Protestants and Jews is up to 9pc on their income tax bills - or about €56 (£45) a month for a single person earning a pre-tax monthly salary of about €3,500, AP reported.

For religious institutions, struggling to maintain their congregations in a secular society where the Protestant Reformation began 500 years ago, the tax revenues are vital.

The Catholic Church in Germany receives about €5bn annually from the surcharge. For Protestants, the total is just above €4bn. Donations, in turn, represent a far smaller share of the churches' income than in the US.

With rising prices and economic uncertainty, however, more and more Catholics and Protestants are opting to save their money and declare to tax authorities they are no longer church members, even if they still consider themselves believers.

"I quit the church already in 2007," Manfred Gonschor, a Munich-based IT-consultant, said. "It was when I got a bonus payment and realized that I could have paid myself a nice holiday alone on the amount of church tax that I was paying on it."

Gonschor added he was also "really fed up with the institution and its failures".

Such defections have hit the Catholic Church especially hard — it has lost about 181,000 tax-paying members in 2010 and 126,000 a year later, according to official figures. Protestants, who number about 24m nationwide, lost 145,000 registered members in Germany in 2010, the most recent year from which figures are available.