Francois Crepeau called on Europe to create a coherent policy on migration
European leaders should do more to open up and help migrants instead of using language that dismisses their rights, a UN expert on migrant rights has said.
Talking about "marauders" and "swarms" was an unsubtle way of dismissing their legitimacy, said Francois Crepeau.
European countries should open official channels and their labour markets to migrants because building fences would not stop them coming, he said.
On Monday, a record number of refugees crossed into Hungary from Serbia.
A total of 2,093 migrants, the highest ever daily total, crossed the border near the town of Roszke, a police statement quoted by AFP news agency said.
Hungary, a European Union member, is erecting a fence to keep out the migrants, with 110km (68 miles) of the 175km fence now in place.
Many of those reaching Hungary are Syrians and Afghans who cross from Turkey to Greece and then make their way northwards.
Lesvos is one of the Greek islands that has been overwhelmed by those arriving, often packed on to flimsy vessels.
Greece's coastguard said on Monday that it had recovered the bodies of two migrants who drowned when their boat sank, while another five were still missing.
More than 33,000 people have landed on Lesvos this month and face "squalid" conditions because of shortages, Amnesty International has said.
Mr Crepeau, the UN special rapporteur on the human rights of migrants, called on the EU to create a "coherent and comprehensive migration policy", making "mobility its central asset".
"Let's not pretend that what the EU and its member states are doing is working. Migration is here to stay," he said in a statement.
"Building fences, using tear gas and other forms of violence against migrants and asylum seekers, detention, withholding access to basics such as shelter, food or water and using threatening language or hateful speech will not stop migrants from coming, or trying to come, to Europe."
There was also an urgent need to create a resettlement programme for 1.5m to 2m refugees, like Syrians and Eritreans, over the next five years, he added.
The UN expert urged Europe to regain control of its borders from the smugglers by offering official channels to enter Europe.
"Opening up the regular labour markets through smart visas allowing people to come to look for work and incentivise them to return if they don't find the job in question would allow for a much better regulated and controlled official labour market," he said.
Europe's commissioner for migration has promised "a war against people smugglers"
He cautioned that such measures should be supported with sanctions against employers who exploit migrants in "underground labour markets" - a proposal being considered in England and Wales.
However, Dimitris Avramopoulos, the EU's commissioner for migrants, has promised a war against smugglers and vowed that migrants who travel to EU countries for economic reasons will be returned.
"The ones who are in need of international protection, they will have it. It is our duty," he told the BBC.