The number of Turkish asylum seekers in Germany has almost doubled so far this year, a development which could undermine the EU’s controversial migrant deal.

The sharp rise will embarrass Angela Merkel, the German chancellor, as she tries to defend Turkey’s role as Europe’s gatekeeper against migrants.

It will also add to growing European criticism of Recep Tayyip Erdogan, Turkey's president, over the repression of democratic freedoms in Turkey.