Denmark has already approved a major decrease in foreign aid and Nordic neighbours Finland, Norway and Sweden -- traditionally generous aid donors -- are now all also preparing major cuts in aid to poor countries in budgets now before their parliaments.
The Netherlands is also looking at shifting funds from development assistance to refugees inside the country.
UN Secretary-General Ban Ki-moon on Wednesday called on governments to confront Europe's worst refugee crisis since World War 2 "without lessening the commitment to vitally needed official development assistance."
"Resources for one area should not come at the expense of another," he said in a statement.
Ban said shifting funds from development aid to refugee assistance was "counter-productive" and would reduce opportunities for millions of people worldwide seeking to build better lives in their home countries.
Nearly 800,000 refugees and migrants have reached Europe by sea this year and hundreds of thousands more have crossed borders, many of whom are fleeing the war in Syria.
"If development aid is siphoned off, then people facing extreme poverty or war will see any chance of improving their lives sharply diminished," the signatories, which included the Lutheran Church, said.