US President Donald Trump has nominated a former military colonel with a history of making Islamophobic remarks to be the next ambassador to Germany. Retired colonel Douglas Macgregor has been put forward by Mr Trump despite his hard-line stance on Muslims. A staunch Trump ally, Col Macgregor has courted controversy over the years after warning that Muslim immigrants were entering Germany "with the goal of eventually turning Europe into an Islamic state". He has also accused Germany of providing welfare benefits to "millions of unwanted Muslim invaders" rather than increasing defence spending. It has been a policy of German Chancellor Angela Merkel to welcome immigrants to the country and has kept Germany’s borders open to refugees amid heavy criticism from her opponents. Col Macgregor was tipped for the position by Mr Trump last month. His nomination follows the resignation of the former US ambassador to Germany, Richard Grenell, in June. Mr Grenell, also a close Trump supporter, had been in the role for two years until he stepped in as the US acting director of national intelligence in the Trump Cabinet in February. Robin Quinville, deputy chief of mission at the embassy, is currently standing in as the ambassador until the new choice is confirmed. Mr Grenell had announced his resignation in a post on Instagram revealing Mr Trump had given him a Cabinet chair as a goodbye present. During his time in the role Mr Grenell advocated the president's "America First" foreign policy vision and also echoed Mr Trump's criticism of Germany's defence spending. Mr Trump's nomination of Col Macgregor has been met with criticism by senior US politicians. "Col Macgregor's public statements over the years on immigration, Muslims and our relationship with Germany should disqualify him for any government office, much less to represent the United States as an ambassador," Bob Menendez, a US senator and the top Democrat on the US Senate Committee on Foreign Relations, told CNN. Col Macgregor has also made comments in support of Russia's ongoing war in eastern Ukraine. The nomination comes at a time when US-German relations have been strained after Mr Trump announced the withdrawal of US troops from the Germany earlier this year.