Growth of Uber's market share among business travelers slowed in the first quarter, and competitor Lyft gained ground against the ride-hailing juggernaut, according to Certify.

Uber accounted for 53 percent of ground transportation expenses that Certify processed in the first quarter, up a single percentage point from the fourth quarter and marking its slowest growth yet. Lyft's share, meanwhile, grew 2 percentage points quarter over quarter to 6 percent.

While some slowing was to be expected considering Uber's market saturation, user reviews and data indicate that some of the negative publicity surrounding the company also factored into the slowed growth, according to Certify. That negative publicity included employee claims of workplace harassment and a viral video of CEO Travis Kalanick arguing with a driver "Lyft is quickly gaining ground, while Uber's growth in the quarter has all but ground to a stop," Certify said. "Time will tell if recent company controversies and negative media coverage have a lasting effect on business traveler perceptions and utilization of Uber."

Despite the slower growth, Uber remained the most expensed brand of any travel category in the first quarter, according to Certify. It accounted for 7 percent of total receipts and expenses, which is three percentage points higher than the next-highest brands, Delta and Starbucks.

Year over year, Uber's share of ground transportation expenses grew 10 percentage points, compared with Lyft's growth of 4 percentage points. Taxis lost 4 percentage points.

Bloomberg reported that Uber's total gross bookings doubled in 2016 to $20 billion. Uber did not release first-quarter data but said revenue was "in line with expectations," according to Bloomberg.

Uber also is working to improve its corporate culture and is searching for a COO to lead some of that change. "Uber must change if it is to be as successful in the next decade as it has been in the last seven years," Uber board member Arianna Huffington said last month. "Going forward, there can be no room at Uber for brilliant jerks and zero tolerance for anything but totally respectable behavior in an equitable workplace environment."