The UNHCR criticized Danish government proposals which would make reunification of refugee families and acquisition of refugee status more difficult.
In a document sent to the Danish government it zeroed in on a measure allowing police to confiscate asylum seekers' belongings worth more than $436 to help pay for their stay which it described as "a deeply concerning response to humanitarian needs" and "an affront to their dignity".
Filippo Grandi, an Italian diplomat who took over as UN High Commissioner for Refugees this week, separately told a news briefing that Europe must set an example by welcoming refugees and not erecting barriers, while sharing the burden fairly across the continent.
He singled out Germany, Turkey and Lebanon for praise for giving asylum to huge numbers of Syrians and other refugees, Reuters reported on Thursday.
More than a million people fleeing wars in the Middle East and Africa arrived in Europe in 2015, with Germany taking in the most. Denmark has now imposed temporary checks on its border after Sweden put in place controls to stop refugees moving further north.
"If Europe had a coherent, coordinated response ... these border reactions that sometimes are justified, like in the case of Sweden by a huge arrival of people, wouldn't be happening," Grandi said.
"We will of course continue to say 'You manage your border as you see necessary', but the right of people to seek asylum should not be jeopardized. That's very, very important."
The European Union must implement its own agreement to improve identification and registration of refugees in Greece and Italy, relocate them equitably across the bloc, and provide humane return for those whose claims are rejected, he said.
Grandi praised the welcoming stance of German Chancellor Angela Merkel, who has come under much pressure to stem the influx and who he said had made "a gesture of leadership" toward the rest of Europe.
"Now if Europe starts setting limits, pushing back, erecting barriers, being hostile, the rest of the world will follow, I can tell you," he said.
The UNHCR would ask countries to take in more Syrian refugees for resettlement at a March 30 conference, but has not yet set a target.
Under the Danish government's proposals criticized by the UNHCR, refugees will have to wait three years before applying to reunify with families abroad.
The duration of temporary residence permits will be shortened, forcing people to reapply, and refugees will be accepted on the basis of their "integration potential" rather than their status solely as refugee.
Most controversial of the measures is that police will have the right to take away belongings and valuables worth more than 3,000 Danish crowns ($436.89) to help fund their stay in Denmark.