Yahoo CEO Marissa Mayer
Yahoo CEO Marissa Mayer is increasingly controversialReuters

Marissa Mayer, the boss of embattled internet giant Yahoo!, fired as many as 30 employees last by accident last week, according to internal rumours. A report in the New York Post suggested that "bureaucratic snafus" left dozens of staff on sacking lists who were not meant to lose their jobs.

It's understood that lists are being composed of underperforming employees who might be removed first, and an anonymous source told the Post that "they put people on firing lists who they didn't mean to". "People who were lower on the performance scale but who weren't meant to get fired," the source claimed. "But no one told the managers, and then they had the conversations, and it was like, 'Oops'."

A spokesperson for Yahoo!, however insisted that "there is zero truth to this rumour".

Yahoo! is a company in trouble, with rumours swirling earlier this month that it would make up to 10% of its workforce redundant. Investors have been angry with the firm's faltering financial performance for a while, and according to one report, want Yahoo! to cut 75% of its staff, focusing only on successful areas like sport and finance, and ditching the rest of its business.

Mayer herself is no stranger to controversy – she has presided over a series of major online acquisitions, including buying the popular blogging platform tumblr for $1.1bn, which have coincided for major falls in Yahoo!'s stock price.

Earlier this month, she upset staff by telling a companywide meeting that there would be no layoffs "this week".

"This is the reason employee morale is so low," an insider told the New York Post. Many staff took this remark as confirmation that Mayer "is sharpening the axe".

Reports have suggested that there is an "invest/maintain/kill" list being prepared on every division of the business. Its offices in Argentina and Mexico have already been closed down.

Yahoo!'s Q4 earnings are due to be posted on Tuesday.