Donald Trump's travel ban will be exploited by far-right and separatist Islamic groups
David Anderson QC issued the warning as the backlash over the American president's immigration crackdown continued.
An executive order signed by Mr Trump on Friday halted the US refugee programme for 120 days, indefinitely banned Syrian refugees, and temporarily suspended the entry of nationals from seven Muslim-majority countries.
Mr Anderson, the Independent Reviewer of Terrorism Legislation, told the Press Association: "The far right and separatist Islamists both promote the myth that Muslims cannot integrate into western society.
"This travel ban will be used by both groups in service of that agenda.
"It sharpens the need for European governments and Muslim communities alike to put beyond doubt their commitment to the integrated societies that nearly all of us want."