Peter Sutherland told peers the future prosperity of many EU states depended on them becoming multicultural.
He also suggested the UK government's immigration policy had no basis in international law.
He was being quizzed by the Lords EU home affairs sub-committee which is investigating global migration.
Mr Sutherland, who is non-executive chairman of Goldman Sachs International and a former chairman of oil giant BP, heads the Global Forum on Migration and Development, which brings together representatives of 160 nations to share policy ideas.
He told the House of Lords committee migration was a "crucial dynamic for economic growth" in some EU nations "however difficult it may be to explain this to the citizens of those states".
'More open'
An ageing or declining native population in countries like Germany or southern EU states was the "key argument and, I hesitate to the use word because people have attacked it, for the development of multicultural states", he added.
"It's impossible to consider that the degree of homogeneity which is implied by the other argument can survive because states have to become more open states, in terms of the people who inhabit them. Just as the United Kingdom has demonstrated."
The UN special representative on migration was also quizzed about what the EU should do about evidence from the Organisation for Economic Cooperation and Development (OECD) that employment rates among migrants were higher in the US and Australia than EU countries.
He told the committee: "The United States, or Australia and New Zealand, are migrant societies and therefore they accommodate more readily those from other backgrounds than we do ourselves, who still nurse a sense of our homogeneity and difference from others.
"And that's precisely what the European Union, in my view, should be doing its best to undermine." » | Brian Wheeler, Political reporter, BBC News | Thursday, June 21, 2012
HT: Roger Savage »
