A co-founder of Twitter has told its 500 million users not to spend hours on the micro-blogging site because it is "unhealthy".

Biz Stone, Twitter's creative director, said users should visit the site for information but leave once they had found it.

At a business conference in Montreal, Canada, Stone, 37, said that using Twitter for hours at a time "sounds unhealthy".

"I like the kind of engagement where you go to the website and you leave because you've found what you are looking for or you found something very interesting and you learned something," he told the Board of Trade of Metropolitan Montreal on Wednesday.

"I think that's a much healthier engagement. Obviously, we want you to come frequently."

The social networking guru, also said there were no plans to increase Twitter's 140-character limit, according to the Montreal Gazette.