Mrs Merkel told a gathering of younger members of her conservative Christian Democratic Union (CDU) party on Saturday that at “the beginning of the 60s our country called the foreign workers to come to Germany and now they live in our country… We kidded ourselves a while, we said: ‘They won’t stay, sometime they will be gone’, but this isn’t reality.

“And of course, the approach [to build] a multicultural [society] and to live side-by-side and to enjoy each other… has failed, utterly failed.”

In her speech, the chancellor specifically referred to recent comments by German President Christian Wulff who said that Islam was “part of Germany” like Christianity and Judaism.

While acknowledging that this was the case, Mrs Merkel stressed that immigrants living in Germany needed to do more to integrate, including learning to speak German.

“Anyone who does not immediately speak German”, she said, “is not welcome”.