The future of Uber CEO Travis Kalanick is hanging in the balance after the embattled cab company’s board voted to adopt a portfolio of recommendations to fight sexual harassment in the firm.

Uber said its board had unanimously approved recommendations – which stem from a report prepared by former US attorney general Eric Holder after a sprawling, multi-month investigation into Uber’s cultures and practices – but declined to reveal what they were until after Uber employees have been told on Tuesday.

One of the first recommendations acted upon was the departure of Emil Michael, vice-president and Kalanick’s deputy. It is not clear whether he resigned or was terminated.

“Uber has a long way to go to achieve all that it can and I am looking forward to seeing what you can accomplish in the years ahead,” said Michael in an email announcing his departure to staff on Monday.

Michael was a close friend and ally to Kalanick and his departure, which comes in the wake of a series of high-profile executives leaving Uber, is a major blow to the CEO as he fights to maintain control of his company.

One move believed to have been under consideration is whether to require a leave of absence for Kalanick, whose aggressive management style has been cited by many as the root cause of the company’s troubles.

In just a few months, Uber – always a controversial company, due to its hostile approach to governmental regulations around taxi businesses and labour laws – has reached new scales of crisis, sparked by a tell-all blogpost from former Uber engineer Susan Fowler. She wrote that she had been propositioned by her boss in a series of messages on her first day of work and that superiors ignored her complaints.

In an internal investigation launched following Fowler’s post, separate from the external one led by Holder, Uber set up a hotline for complaints: more than 200 were registered, leading to more than 20 employees being terminated. Those terminations came just three weeks after Uber’s head of Human Resources, Liane Hornsey, had told USA today that sexual harassment “didn’t come up as an issue”.

The past year has been one of intense public disquiet at various Uber scandals. Photograph: Michael N/Pacific/Barcroft Image

Kalanick, 40, has acknowledged his management style needs improvement. He said earlier this year he needed to “fundamentally change and grow up”, even as he celebrated a valuation of almost $70bn for the Oakland-based firm, founded in 2009 as UberCab.

But even his attempts at change, backed by Uber investor and board member Arianna Huffington, have led to their own problems. Huffington argued that Kalanick is growing as a person, telling a CNBC conference that “last week when we were in the office and he said, ‘I really need to go meditate in order to be in a place to make good decisions right now. And literally [he] went into a lactation room that happened to be open because they don’t have meditation rooms yet. This is part of the change coming.” That sparked a new wave of anger at the executive’s casual disregard of the needs of his employees who are nursing mothers.

If Kalanick does get asked to temporarily step away from the firm, he may also return to a role with less authority. But asking the executive to step down entirely is almost impossible for the board. Uber has a large concentration of voting rights in the hands of a small number of people, including Kalanick. The board is comprised of nine people, seven of whom hold “super-voting shares”, allowing them more of a say; of those seven, Kalanick and a number of allies, such as co-founder Garrett Camp and Huffington, hold a majority. Four director seats at the firm are empty.

The company also plans to appoint Wan Ling Martello, an executive vice president at Nestlé SA, to the board, Bloomberg reported on Monday, citing people familiar with the matter. One Uber investor called the board’s decisions on Sunday a step in the right direction, giving Uber an “opportunity to reboot”.

Sexual harassment is not the only issue the company has to face up to, however. Last week it was reported that a senior executive obtained the medical records of a woman who was raped by an Uber driver in India. The executive, who shared the victim’s medical details with Kalanick, believed the rape case could have been part of a conspiracy by one of Uber’s Indian rivals, even though the Uber driver was found guilty and sentenced to life imprisonment.

The ride share firm has been threatened by boycotts, sued and is the subject of a federal investigation into using a fake version of its app to stop authorities looking into whether it was breaking local laws.

Kalanick also lost his temper earlier this year in an argument with an Uber driver who was complaining about pay, with Kalanick’s profanity laced comments caught on video.