A bitter fight over control of Uber has intensified in recent days with warring factions battling over the future role, if any, of ousted chief executive Travis Kalanick at the global rideshare titan. On Monday, a major investor fired off a message to Uber employees explaining why it filed suit last week against founder Kalanick, accusing him of covering misdeeds while rigging the board in order to return to power at the company. Benchmark Capital Partners said in the letter it acted to push Kalanick out due to "a deep conviction that it would be better for Uber, its employees, and investors to have a fresh start."

The letter said the company needed to clean up "utterly unacceptable" behavior at the company, which has been roiled by disturbing reports of a cutthroat workplace culture, harassment, discrimination and questionable business tactics to thwart rivals. It added that Kalanick failed to live up to his promises when he quit as CEO in June and that he may be manipulating the search process for his replacement to "create a power vacuum in which Travis could return." The suit filed by Benchmark accused Kalanick of committing fraud, breach of contract, and violating fiduciary duty by conniving to "entrench himself on Uber's board of directors and increase his power for his own selfish ends."

The company which calls on a Delaware court to bar Kalanick from tinkering with the Uber board. Shareholders loyal to Kalanick meanwhile have asked Benchmark to sell its shares and have nothing to do with the Uber board of directors. In a letter to Benchmark last week, investors siding with Kalanick accused the company of hurting Uber by holding "the company hostage to a public relations disaster" by calling for his resignation on short notice "and within weeks of a personal tragedy, under threat of public scandal."

The letter signed by early Uber "angel" investor Shervin Pishevar and others asked Benchmark to sell enough shares to surrender board appointment rights, saying it had people ready to buy the stake. An early investment of $27 million made in Uber by Benchmark was now estimated to be worth some $8.4 billion. Uber is not listed on a public exchange, so its value is determined by how much private investors pay for stakes in the company.

Meanwhile, a New York Times report on Monday indicated that Uber's board is selling shares in the San Francisco-based company at a discount from Uber's estimated $68 billion value with one of the scenarios allowing Benchmark to take its money and leave. One of the reported offers is from Japanese banking giant SoftBank and the other from a consortium of investors led by Dragoneer Investment Group.