The EU should "do its best to undermine" the "homogeneity" of its member states, the UN's special representative for migration has said.
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".