The Government Pension Fund of Norway, as the fund is officially known, overtook Abu Dhabi's sovereign wealth fund in 2012 to become the world's largest. But it has come under criticism for what some see as its overly cautious investment strategy and relatively low returns, with some politicians in Norway calling for it to be split up.
"It needs to be double the size and larger, so we are recruiting actively,” Mr Johnsen said. "This group will expand quite a lot going forward. We’re still in a build-up phase."
He said he was particularly looking to hire experts in sectors such as US banks and European insurers.
"In terms of how we’ve picked [which sectors to focus on] it’s based on who we recruited, but it’s also based on where we think we can utilise the fund’s characteristics to the best extent possible and maybe also where we actually have had success,” Johnsen said.
The fund at present has 85-90 people in its equity unit based around four divisions: one comprising sector specialists, another dealing with special situations, such as initial public offerings, another looking at global equities, and the last one running training programmes.
Johnsen told the paper that despite the fund's size, with $540bn invested in equities, he believed he had shown it was “fully capable of managing a large fund”.