GENEVA — An independent UN investigator into the human rights of migrants has postponed an official visit to Australia that was due to begin on Sunday, citing a lack of government cooperation and “unacceptable” legal restrictions. Asylum seekers have long been a lightning-rod political issue in Australia, although it has never received anywhere near the number of refugees currently flooding into Europe from war-ravaged areas of the Middle East and North Africa. UN Special Rapporteur Francois Crépeau had planned to gather first-hand information about the situation of migrants and asylum seekers in the country and in Australian off-shore detention centers in neighboring Nauru and Papua New Guinea. He had asked for access since March but Australia denied him access to any offshore center, he said in a statement. Crépeau also blamed Australia's 2015 Border Force Act, which discourages detention centre service providers with the threat of a two-year court sentence if they reveal “protected information,” for preventing him from doing his job. “This threat of reprisals with persons who would want to cooperate with me on the occasion of this official visit is unacceptable,” Crépeau said in the statement. He had asked Australia to guarantee in writing that nobody helping him would suffer reprisals but the Australian government refused, the statement said. The Australian government said on Saturday the decision was “disappointing and unfortunate.” “The government accommodated to the fullest extent possible the requests of the office of the special rapporteur as it has with past visits,” a spokesman for Immigration Minister Peter Dutton said in a statement. “Access to regional processing centres in Papua New Guinea and Nauru is the responsibility of these sovereign nations and needs to be addressed with their governments. Australia remains ready to arrange a future visit by the special rapporteur.” Prime Minister Malcolm Turnbull said on Wednesday he was “concerned” about Australia's controversial offshore immigration detention centers, although he stopped short of committing his government to reconsidering them. Australia has vowed to stop asylum seekers reaching its shores, turning boats back to Indonesia when it can and sending those it cannot for detention in camps on Manus island in impoverished Papua New Guinea and on Nauru in the South Pacific. The United Nations and human rights groups have criticized Australia over conditions at the camps and its tough asylum-seeker policies, which Turnbull's predecessor Tony Abbott defended as necessary to stop deaths at sea and often described as one of his government's biggest achievements. — Reuters