Image copyright YASUYOSHI CHIBA Image caption UN Environment executive director Erik Solheim

The head of the UN body that leads on sustainability and green issues has been criticised for extensive and expensive air travel.

A draft internal audit, obtained by the Guardian and seen by the BBC, says that Erik Solheim's actions risked the reputation of UN Environment.

The report says he incurred costs of $488,518 (£373,557) while travelling for 529 out of 668 days.

There was "no oversight or accountability" to monitor this travel.

Mr Solheim says he has paid back the money where "instances of oversight" occurred.

Missing reports

The audit was carried out by the UN's Office of Internal Oversight Services (OIOS).

Across UN Environment, around $58m was spent on travel in the two years up to 2018.

OIOS points out that the amount of money UN Environment spends on travel essentially doubled over the three years between 2014 and 2017.

While all UN staff are expected to complete "mission reports" within two weeks of travel, OIOS found that these were often missing.

When they requested reports for 596 trips undertaken by 32 managers and staff, 210 mission reports were not provided, while around 200 others were only completed after the request was made.

The report is particularly critical of the travel undertaken by Mr Solheim, UN Environment executive director since 2016 and former Norwegian environment minister.

According to OIOS Mr Solheim's leave and travel were approved by a member of his office who reported directly to him, in contravention of UN rules.

The report says that Mr Solheim travelled extensively across the continents, making several trips and stops in Paris as well as Norway. On one occasion, "he made an eight-hour trip from Washington DC for a weekend in Paris, before taking another flight to New York city."

The draft audit says the senior management at UN Environment "fostered an organisational culture that defied established internal control systems".

Image copyright TONY KARUMBA Image caption Mr Solheim has been a strong advocate for ending plastic pollution

After one request by a UN official for more information about a trip to his home country, the report says that Mr Solheim responded: "We cannot accept this question on holiday vs job. Please tell UN Nairobi it is totally irrelevant..we are not any longer living in the industrial age and they must stop treating me as if I am a 07 to 16 factory worker...the other side of this coin is that they must stop asking this stupid question".

The pattern of travel among senior management, said the auditors, was contrary to the ethos of carbon emission reduction. The report highlighted the former UN Secretary General's statement that "what we demand of others, we must do ourselves."

Environmentalists in Norway said the audit the report was "ironic and sad".

"I strongly believe even UN bodies, as well as everyone else, should be aware of their environmental impact and have policies and routines to reduce them," said Truls Gulowsen, from Greenpeace.

"Solheim has been a very visible UN Environment leader, which is good and clearly warrants travel, but this volume and attitude towards environmental footprints does not set a positive example."

In a statement, Mr Solheim said he wasn't able to comment in detail on the audit as it was a confidential process, but that he had paid back any money owed.

"The Office of Internal Oversight Services earlier this year investigated all my travels in great detail and found three instances of oversight out of all of them. The money was refunded immediately. If any other mistakes are found, we will immediately correct them.

"Where questions have been raised about the authorisation of my travel it should be noted that we have immediately put new procedures in place whereby my travel is approved by the office of the Secretary General."

"Let me underscore that we will work diligently and without question to implement the auditor's recommendations in the final report, and that we welcome any audit process and external oversight that helps improve operational efficiency."