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There were too many trips to Paris. And it wasn’t helping to save the environment.

That was among the conclusions of an internal audit that resulted in the resignation Tuesday of Erik Solheim, a veteran Norwegian diplomat, from his post as head of the United Nations Environment Program. The investigation, conducted by the United Nations Office of Internal Oversight Services, criticized the environment agency for “a culture of scant regard for internal controls and existing rules” on the use of public funds.

Mr. Solheim said in a statement he had decided “with a heavy heart” to step down after receiving the final audit results on Saturday. He admitted no wrongdoing and, in a statement, said that he remained “committed to doing what I believe to be in the best interest of U.N. Environment and the mission we are here to achieve.”

The United Nations secretary general, António Guterres, without mentioning the audit, said Tuesday he had accepted Mr. Solheim’s resignation. In a statement later in the day, Mr. Guterres described Mr. Solheim as “a leading voice in drawing the world’s attention to critical environmental challenges.”

The scrutiny of Mr. Solheim and his travel expenses came at a time of shrinking resources at the world body, so much so that some donors to the environment program decided to withhold funds pending the final audit results.