A fund managed by the descendants of oil tycoon John D Rockefeller announced on Wednesday the fund's intent to divest itself from fossil fuels in a statement that criticized the US energy giant ExxonMobil for "morally reprehensible conduct."

The New York-based Rockefeller Family Fund said it was proud to announce its intent to divest from fossil fuels, adding that the process will be completed as quickly as possible. The action is part of a broader offensive by the fund against fossil fuels.

"While the global community works to eliminate the use of fossil fuels, it makes little sense - financially or ethically - to continue holding investments in these companies," the fund said in a news release. It also was highly critical of ExxonMobil, saying there was evidence that appears to suggest ExxonMobil has worked for decades to confuse the public about climate change.

The oil company is being investigated by the New York attorney general on suspicion that it lied to the public and investors by manipulating study results about the effects of climate change, according to media reports in November.

An ExxonMobil spokesman said it was not surprising that the fund would divest itself of ExxonMobil stocks "since they're already funding a conspiracy against us." The spokesman also said the Rockefeller Family Fund has provided financial support to media outlets that "produced inaccurate and deliberately misleading stories about ExxonMobil's history of climate research." ExxonMobil believes the risk of climate change is clear and warrants action, the spokesman said in an email. The fund's decision follows a similar move by the larger Rockefeller Brothers Fund, which announced in September 2014 that it would gradually separate from investments in the segment.

The decisions by the funds are noteworthy because of the history of the Rockefeller clan. The oil business made the family one of the richest in the world, with a fortune dating back to industrialization in the late 19th century.

The fund acknowledged the irony and said because of its long and profitable history investing in the oil industry, divestiture was not decision that it had taken lightly. "But history moves on, as it must," the fund's statement said. "It is past time for all people of good will to do everything in their collective power to make our new path one that recognizes the deep interdependence between humanity's future and the health of our natural systems."