Yahoo's Marissa Mayer 'oversleeps and misses posh dinner with top execs' at Cannes Lions

The Yahoo CEO also came under under scrutiny from WPP's Martin Sorrell who questioned her e-mail etiquette and her relationship with Dan Loeb

'Corporate America’s most celebrated working mother': Marissa Mayer, CEO of Yahoo! (AP)

A transatlantic flight, even if you're flying first class, can be a difficult thing to deal with. Just ask Yahoo's chief executive Marissa Mayer.

Last week, the 39-year old descended on the French Riviera to attend this year's Cannes Lions, the world's biggest get-together for the advertising industry, where she was supposed to sing the praises about Yahoo's new and improved strategy.

Unfortunately, Mayer showed up "nearly two hours late" to a fancy private dinner organised by Interpublic Group, a major advertising holding group, where she was expected to meet top marketing executives and IPG's CEO Michael Roth because she was too tired and overslept, the Wall Street Journal reports.

"If it were an investor meeting, a board meeting or a potential acquisition, I am sure she or someone from her team would have woken her up," one top executive told the newspaper. "It is another instance where she demonstrated that she doesn't understand the value of clients, ad revenue or agencies."

Video: Yahoo's Marissa Mayer 'oversleeps and misses posh dinner'

Mayer, who is often described as one of the most powerful women in the male-dominated tech sector, was also criticised for her poor presentation skills at the event. An unnamed source told Business Insider she "basically read her entire presentation from teleprompter screens" and looked forced and stiff.

The Yahoo CEO was also reprimanded by Sir Martin Sorrell, CEO of WPP, the global advertising giant, for not returning his e-mails unlike Sheryl Sandberg, Facebook's COO, who always gets back to him.

Asked about her relationship with hedge fund manager Dan Loeb, she insisted they are on "very good" terms, but Mr Sorrell questioned her remarks, adding: "That's not what Dan tells me."

A spokesperson for Yahoo said the company values its partnership "with IPG and all of our advertisers."