Richard Falk, the U.N. special envoy, said he was calling on the international community to take the necessary steps to ensure Palestinian rights are protected.
"Special steps must be taken to ensure that the human rights of the Palestinian people are protected and the rule of law established in an occupation which has lasted now for more than 45 years," he said in a statement.
Falk said the number of Israeli settlements built in the West Bank doubled last year. Already, there are "hundreds" of new settlements approved in the area this year by the Israeli government.
A so-called separation barrier was declared illegal by the International Court of Justice in 2004. At least 80 percent of the planned route is inside the West Bank and construction is 60 percent completed, he said.
"Such a course of action undermines respect for international law and should be challenged," he said.
U.S. Secretary of State John Kerry, working toward a peace agreement between the Israelis and the Palestinians, has said the settlement activity was counterproductive.
Falk presents his final report on the situation Monday to the U.N. Human Rights Council.