Twitter’s revenue leapt by 61 per cent year on year to $502.38 million for Q2 2015, but the company’s co-founder and interim CEO Jack Dorsey is “not satisfied” with user growth.

The company exceeded its own top revenue guidance of $485 million for the quarter. Monthly active users reached 316 million, up 15 per cent year-on-year.

But Twitter noted that “the vast majority” of monthly active users gained during the quarter (8 million) came from the its SMS Fast Followers service, which does not require a Twitter account to use.

Without this, core active users only grew by two million quarter-on-quarter, to reach 304 million, its slowest rate yet.

In a statement, Dorsey said the company’s Q2 results showed good progress in monetising the service, but he was still not happy with user growth.

“We are not satisfied with our growth in audience,” he said. “In order to realise Twitter’s full potential, we must improve in three key areas: ensure more disciplined execution, simplify our service to deliver Twitter’s value faster, and better communicate that value.”

Speaking after the results, Twitter’s CFO Anthony Noto revealed it plans to launch a marketing campaign by the end of the year, aimed at teaching people how to use the platform.

He however warned that the firm did not expect to see meaningful growth until it reaches a mass market audience, which could take considerable time.

Net loss down

Twitter, which is yet to post a profit as it continues to spend on expanding its service, said its net loss also narrowed by 5 per cent, to $136.66 million from $144.64 million year on year.

The bulk of its revenue growth came from advertising, increasing 63 per cent to  $452 million, while data licensing and other revenue increased 44 per cent year on year to $50 million.

For the US, Twitter posted total revenue of $321 million, an increase of 53 per cent from Q2 2014. International revenue increased 78 per cent year-on-year to $181 million.

These Q2 results are the first to be released by the company since the departure of Dick Costolo earlier this month, who held the top position since the company first went public in 2013. He left amid investor pressure over poor user growth.

A permanent successor has yet to be appointed, but the improved numbers may strengthen the position of the company’s head of revenue, Adam Bain, who is also reportedly vying for the top job with Dorsey.

According to technology site Recode, Twitter’s board is now leaning towards an internal recruitment after struggling to identify an appropriate external candidate.