Twitter chief executive Dick Costolo has announced he is stepping down - with the site's co-founder, Jack Dorsey, replacing him.

The social media network has struggled to boost its numbers of users, despite a high-profile public offering on the stock exchange two years ago.

In a statement, Twitter said Dorsey's role would be temporary while a permanent CEO was found.

Speaking about his decision to leave, Mr Costolo said, “I am tremendously proud of the Twitter team and all that the team has accomplished together during my six years with the Company.

"We have great leaders who work well together and a clear strategy that informs our objectives and priorities. There is no one better than Jack Dorsey to lead Twitter during this transition," he added.

Jack Dorsey paid tribute to Costolo, saying “the future belongs to Twitter thanks in large part to Dick Costolo’s dedication and vision. Dick has put a world-class team in place and created a great foundation from which Twitter can continue to change the world and grow."

Twitter say they expect their second quarter revenue to be in the $470 million to $485 million range.

Earlier this year the social network had seen higher revenues but less monthly users.