Dick Costolo has resigned as Twitter CEO, the social messaging company has announced.

Twitter’s co-founder Jack Dorsey will take over as interim chief on July 1 and stay until a replacement can be found.

Dick Costolo had been under pressure from investors unhappy with the company’s user growth.

In a statement, Dick Costolo said he was “tremendously proud of the Twitter team”.

Twitter said that its board had formed a committee to undertake the task of finding a successor.

Following the announcement, Twitter shares jumped by more than 7% in trading after US markets had closed.

Twitter debuted on the NYSE in 2013 but has not been adding users as fast as investors had hoped.

In April, Twitter missed Wall Street’s forecasts for revenue growth and posted a net loss of $162 million.

Its share price has declined nearly 30% since then, and is currently trading below the price it debuted at in 2013.

Analysts remain pessimistic about the company’s ability to grow.

The research consultancy eMarketer estimates that Twitter’s monthly user base will grow just 14.1% this year, slowing from more than 30% two years ago.

By 2019, eMarketer says Twitter’s user growth rate will be just 6% worldwide.

Announcing his resignation, Dick Costolo said in a statement: “I am tremendously proud of the Twitter team and all that the team has accomplished together during my six years with the company.”

On a conference call to discuss the move, Dick Costolo added that he had decided to go now because he felt the continued scrutiny if he remained would be a “distraction” and of “no help to the company”.

Questioned on what the board was looking for in its next chief executive, Jack Dorsey said the search team would take as long as necessary, the candidate could come from inside or outside the company but added the one criteria they knew for sure: he or she should be a Twitter user.

Jack Dorsey said the most important attribute was that they “really use and love the product in every single way”.

Dick Costolo will remain on the board of the company. He has been a director since September 2009 and became CEO in October 2010.