The US president claimed refugees and migrants has “strongly and violently” changed European culture and said the continent had made a “big mistake” in giving sanctuary to those fleeing conflicts in the Middle East and Africa.
Without specifically naming the Germany chancellor but instead pointing the blame at Germany’s “leadership” he said: “The people of Germany are turning against their leadership as migration is rocking the already tenuous Berlin coalition.
“Crime in Germany is way up. Big mistake made all over Europe in allowing millions of people in who have so strongly and violently changed their culture!”
Mr Trump is wrong to say that crime in Germany has increased; the latest figures released last month show it has now reached a 30-year low.
Ms Merkel is embroiled in a domestic political row with her conservative allies over how to handle new refugee arrivals, with one of her most senior ministers calling for a more restrictive policy.
The Chancellor bought time on Monday by getting her interior minister Horst Seehofer, to agree to pause the roll-out of a harsher policy until after a meeting of European leaders in Brussels later this month.
Mr Seehofer, a Bavarian conservative who has the backing of his local state government, wants refugees who have already registered in another country to be turned away at Germany’s borders.
The Chancellor however reportedly wants any change in refugee or migration policy to be conducted at a European level, fearing that Germany going it alone could result in a free-for-all of countries enacting a patchwork of contradictory approaches.
Migration is set to be a major discussion point at the European Council meeting on 28 and 29 June, with the issue a major priority of Austria’s right-wing government, which holds the rotating presidency of the pan-EU body.
The US president’s intervention could be useful for Ms Merkel because he is very unpopular in Germany; just 11 per cent of Germany has a favourable view of him, according to research by pollster Pew for the Germany public broadcaster DW.