Ban Ki-moon, the United Nations secretary-general, is facing a revolt by the union that represents his 8,000 staff over issues that range from possible exposure to asbestos to a potential terrorist threat against buildings it will soon occupy in midtown Manhattan.

After the UN staff union adopted four resolutions in the space of two months on safety and security, its head has now accused Mr Ban of being the most unresponsive secretary-general in the UN’s 63-year history for his failure to respond to the concerns.