LONDON (Reuters) - The CEO of the Science Based Targets Initiative (SBTi), the global non-profit at the centre of a public tussle over whether and how companies should be allowed to offset their carbon emissions, has resigned, it said on Tuesday.

Luiz Amaral, who joined SBTi in February 2022, told the board he planned to step down for personal reasons, it said in a statement, adding he would leave at the end of July.

Chief Legal Officer Susan Jenny Ehr will take over as interim CEO, and a search process for a permanent CEO has begun, it added.

The announcement follows criticism of Amaral and the SBTi leadership team from its staff and a group of climate experts after the board of trustees announced in April a plan to allow companies to offset greenhouse gas emissions from their supply chain with carbon credits.

Supporters said the move was crucial to help encourage ambitious companies to decarbonise faster, while critics said it was more important to stop emitting in the first place, something offsetting could discourage.

After the original board announcement, a number of SBTi staff called for Amaral to resign, while various groups sent letters in support of both sides of the argument, which prompted the board to clarify its position.

Holger Hoffmann-Riem from Swiss NGO Go for Impact, who is also a member of the SBTi Technnical Advisory Group (TAG), said the credibility of SBTi had suffered tremendously since its board said it would allow the use of carbon credits.

"For SBTi to regain its credibility, we need a fresh start, with a new board, a new governance structure, and a new CEO," he said.

Kaya Axelsson, research fellow at Oxford who is also a member of the TAG, said Amaral's resignation did not alleviate concerns about SBTi's board governance.

Once these issues are addressed, SBTi could still play a key role in incentivising companies to meet their net zero targets and to contribute to decarbonising the global economy, she added. "Now is not the time to abandon ship on SBTi," she said.

At the time of Amaral's resignation, the SBTi staff were in the process of analysing responses to a public consultation on the use of offsets that was undertaken last year, with the results due to be delivered in July.

An early draft of the analysis, seen by Reuters, indicated that the review found much evidence that offsets are largely ineffective.

(Editing by Robert Harvey, Emelia Sithole-Matarise and Jan Harvey)

By Simon Jessop and Virginia Furness