S&P Dow Jones Indices has removed electric carmaker Tesla Inc from its widely-followed S&P 500 ESG Index, citing issues including racial discrimination claims and crashes linked to its autopilot vehicles, a move that prompted critical tweets from Tesla CEO Elon Musk on Wednesday.

Other contributing factors to the changes, effective May 2, included Tesla's lack of published details related to its low carbon strategy or business conduct codes, said Margaret Dorn, the organization's head of ESG indices for North America, in an interview.

Even though Tesla is contributing to reducing emissions with its electric cars, Dorn said, its issues and lack of disclosures relative to industry peers should raise concerns for investors looking to judge the company across environmental, social and governance (ESG) criteria.

"You can't just take a company's mission statement at face value, you have to look at their practices across all those key dimensions," she said.

Tesla representatives did not immediately respond to questions. But after the index changes, Tesla CEO Elon Musk tweeted on Wednesday that "ESG is a scam. It has been weaponized by phony social justice warriors."

The back-and-forth underscores a growing controversy about how to judge corporate ESG performance. Investors concerned about issues like diversity and climate change have poured money into funds using ESG criteria to pick stocks, prompting questions about how effectively the funds promote change or whether they have become too involved in setting policy.

S&P Dow Jones Indices is majority-owned by S&P Global Inc..

The removal Tesla was among a group of changes made to the S&P 500 ESG Index dating from April 22, according to an announcement. Among the additions to the index at the same time was Twitter Inc, the social media platform Musk has under agreement to purchase.

Dorn and others did not immediately describe the reasons Twitter was added.