The United Nations’ environment chief resigned Tuesday after receiving the results of an audit that had reportedly found that he spent almost $500,000 on travel in less than two years.

U.N. Environment (UNEP) Executive Director Erik Solheim, a former Norwegian diplomat, said in a statement that he had received the final reports on the audit of his official travel by the U.N.’s Office of Internal Oversight Services (OIOS) and was stepping down.

“It is my most sincere hope that this proves to be in the best interest of U.N. Environment and the wider U.N.” he said.

The audit has not yet been released by OIOS, but The Guardian reported in September on a draft audit that found that he was travelling for 529 days out of the 668 days audited, and spent $488,518 on travel. The audit was reportedly particularly critical of his frequent flying -- including a weekend trip from the U.S. to France and back. It found that such travel "presents a reputation risk to the organization, especially [given] that UNEP is supposed to be the lead on sustainable environment matters.”

It also reportedly found that he had “no regard for abiding by the set regulations and rules” and claimed unjustified expenses. The audit reportedly said Solheim did not provide justification for 76 days spent in Oslo and Paris on travel, and he was criticized for allowing two managers to work unofficially from Paris, rather than UNEP headquarters in Nairobi.

Solheim told the outlet that he had paid back money and made changes where rules had been broken.

“If administrative rules are found to have been overlooked, I accept personal responsibility and offer my unflinching commitment to refining a process that prevents them from ever occurring again,” he said at the time.

Secretary-General Antonio Guterres said in a statement Tuesday that he was grateful for Solheim’s service “and recognizes that he has been a leading voice in drawing the world’s attention to critical environmental challenges, including plastics pollution and circularity; climate action; the rights of environmental defenders; biodiversity; and environmental security.”

Guterres said that Deputy Executive Director Joyce Msuya will be acting director while a recruitment process is launched for a successor -- a process that will include discussions with member states.

HALEY: NO TO UN GLOBAL PACT FOR THE ENVIRONMENT

The United Nations has been a central arena in the international fight over environmental regulations for years, where there has been significant pushback from the U.S. In May the U.S. rejected supporting a proposal for bringing international environmental law under one legally binding treaty at the U.N. The Global Pact for the Environment would consolidate what it called the "fragmented nature of environmental law" and "codify" it.

In a statement to Fox News, U.S. Ambassador to the U.N. Nikki Haley said that, “When international bodies attempt to force America into vague environmental commitments, it’s a sure sign that American citizens and businesses will get stuck paying a large bill without getting large benefits. The proposed global compact is not in our interests, and we oppose it."

Fox News' Ben Evansky contributed to this report.