CANNES, France (Reuters) - WPP (>> WPP Group) and Publicis (>> Publicis Groupe) said on Friday the world's biggest annual advertising industry conference in Cannes had become costly, too scattered and should return to its roots of solely promoting agencies' creativity.

The criticism highlights the frustration of the world's number one and number three advertising groups as deep-pocketed tech giants such as Facebook (>> Facebook) and Alphabet's (>> Alphabet) Google have been taking a greater part in the event, first held in 1954 to exhibit advertising films.

"Cannes has to change," WPP's chief executive Martin Sorrell told Reuters.

"If we would be starting the concept again today, what would we do differently?" he added, saying he would prefer it if the conference took place in another city and at another time.

WPP's boss floated the idea that his group could consider not participating in the festival, following the stir caused by his counterpart at Publicis, Arthur Sadoun, who decided to skip the event altogether next year to focus on the development of a collaborative internal network, dubbed "Marcel".

"...We're shifting our promotional budget to reinvest in our people and the future of our company," Sadoun said in the memo, sent to the group's 80,000 employees on Thursday.

"So, we are taking a pause from awards shows, festivals and industry events for 365 days," he added.

His predecessor, Maurice Levy, now chairman, pointed to the high costs of the Cannes event, which he says is now more focused on networking and business than on agencies' products.

"There are many excesses and a lot of spending," Levy told Reuters. "(This trend) is dominated by tech companies at a time when we are being asked to be more frugal by advertisers."

In response to the criticism, event organizer Ascential (>> Ascential PLC) said in a statement it would create an advisory committee to "help shape the future of the festival and ensure it continues to respond to the needs of the industry".

(Editing by David Evans)

By Mathieu Rosemain

Stocks treated in this article : Publicis Groupe, Facebook, WPP Group, Alphabet, Ascential PLC