Former Uber CEO Travis Kalanick is skewering a lawsuit filed by a former ally, describing it as a malicious attempt to sever his remaining ties to the widely used ride-hailing service that he co-founded.

Kalanick lashed out in legal documents filed late Thursday in response to a Delaware Chancery Court lawsuit filed against Uber last week by one of its major investors and a former Kalanick supporter, Benchmark Capital.

The acrimony sets the stage for what could be a bitter battle pitting the pugnacious Kalanick against Benchmark, a major Silicon Valley venture capital firm. Benchmark has seen its 2011 investment of $12 million in Uber grow into a stake now worth more than $7 billion, based on recent valuations of the company.

Uber is being thrust into the crossfire at a time it is trying to recover from revelations of rampant sexual harassment within the company and allegations that it stole trade secrets from a Google spin-off, Waymo, to build self-driving cars. The San Francisco company is also still looking for a new CEO to replace Kalanick, who resigned in late June under pressure from Benchmark and other investors worried about Uber's direction.

Benchmark alleges Kalanick has been interfering in the CEO search and manipulating Uber's board in a scheme to bring him back as the company's leader.

After his resignation as CEO, Kalanick re-appointed himself to Uber's board as part of special powers that gives him control over three board seats. Benchmark now wants those powers taken away, contending they were given to Kalanick under false pretenses.

In his filing, Kalanick contends that Benchmark had secretly plotting against him, and launched its plan to oust him from Uber "at the most shameful of times" -- shortly after his mother was killed and his father critically injured in a boating accident on May 27.

Benchmark had no comment on Kalanick filing, referring back to an earlier statement explaining that the firm felt it had no other choice but to sue to stop unacceptable behavior at Uber.

Kalanick notified Uber of his plans to take an indefinite leave of absence as CEO on June 11 -- two days after his mother's funeral. Uber's board, including Benchmark partner Bill Gurley, supported that move and assured him he could return as CEO whenever he was emotionally ready, according to Kalanick's filing.

But just nine days after he went on leave, Benchmark partners Peter Fenton and Matt Cohler came to Kalanick's hotel in Chicago to demand that he submit his permanent resignation as CEO, the filing said. If Kalanick refused, Fenton and Cohler threatened to sully his reputation in a public campaign, according to the filing.