UN environment chief Erik Solheim has resigned after a report found he had claimed almost $500,000 in air travel and hotel expenses in 22 months.

The internal UN report revealed that Mr Solheim, a former Norwegian environment minister, had travelled excessively at a time of budget cuts at the world body.

He has been accused of disregard for the environmental impact of aviation carbon emissions, after travelling on 529 of the 668 days covered in the Office of Internal Oversight Services (OIOS) audit leaked to the Guardian in September.

The report said Mr Solheim’s expenses were a “reputation risk” for an organisation dedicated to combating climate change.

UN spokesperson Stephane Dujarric confirmed that Secretary-General Antonio Guterres had accepted Mr Solheim's resignation on Tuesday, and that it would take effect from Thursday.

Mr Dujarric said: "The Secretary-General, I think, is pleased to see that UNEP (the UN Environment Programme) is committed to implementing the recommendations that are found in the OIOS report on the travel office."

After two years as executive director of the Nairobi-based UN Environment Programme, Mr Solheim said: "I have been and remain committed to doing what I believe to be in the best interest of UN Environment and the mission we are here to achieve." He said that "after deep reflection" over his expenses, he needed to step down.