European science bodies on Thursday criticised Donald Trump's administration for what they said was a "policy reorientation" in favour of views "not based on facts and sound scientific processes and evidence."

A letter signed by 46 scientific organisations urged Europe's politicians to defend the principles and values that have traditionally underpinned scientific progress -- including the open exchange of people and ideas.

Principles such as transparency, information-sharing and the physical mobility of scientists were vital to scientific development and the benefits they bring to societies and economies, the letter said.

The authors cited the new US president's attempts to ban travellers from seven Muslim-majority countries and threats to stop government scientists from talking to the press or publishing findings without permission.

They were particularly concerned, the group said, about "the unwarranted credibility to views not based on facts and sound scientific processes and evidence in areas such as climate science or the safety of vaccines."

There was no place in modern science for restrictions on research in "inconvenient areas", the letter said.

"Our colleagues working in the US will suffer, the United States and US citizens will pay a price, as will Europe and Europeans, and countries and people all across the globe."

Now more than ever the world needs solid science and research to address "unprecedented challenges," the letter added.

Signatories included the British Royal Society, the science academies of Switzerland, Sweden, Denmark and the Netherlands, the European University Association and EuroScience, an association of researchers.

It was sent to the heads of the European Council and European Commission Donald Tusk and Jean-Claude Juncker, EU science commissioner Carlos Moedas, and the premiers and science ministers of all EU member states and of Norway, Switzerland, Iceland and Serbia.

The letter was dated to coincide with Thursday's opening the annual general meeting of the American Association for the Advancement of Science in Boston.