The British economic model is broken. This contention is now regularly made by the left and the more thoughtful parts of the right. The New Economics Foundation (NEF) is in the enviable position of having argued as much for decades. Its vision of a more sustainable and egalitarian economy has rarely felt more relevant.

One recent afternoon I visited NEF’s offices in Salamanca Place, London, to meet chief executive Miatta Fahnbulleh, who took over in November 2017. Fahnbulleh, 38, who succeeded Marc Stears, a former aide to Ed Miliband, is the first black person to lead a major think tank and appears pleasantly surprised when I point this out. “I think you might be right! That’s incredible. I’ll take that!”

Her first year in the role will be even more frenetic than anticipated. Fahnbulleh, who is married with one son, is expecting twins and will take maternity leave from May until the autumn. But she is energised by the challenge confronting NEF.

“We’ve been saying the economy doesn’t work,” she said (average real wages, for instance, are not forecast to return to their pre-crisis peak until 2025). “But there isn’t necessarily a sense of what the alternative looks like… Our job is to start articulating that.”

A new economy, Fahnbulleh, told me, should be founded on six pillars: respecting environmental limits; higher living standards and greater income equality; new models of ownership (such as co-operatives and mutuals); progressive businesses and stronger corporate governance (“moving away from the short-term drive for profit maximisation”); an interventionist and radically decentralised state; and greater citizen participation.

NEF styles itself as “the only people-powered think tank”. It has recently started or completed 74 local projects such as building a community-owned harbour for fishermen in Eastbourne, working with taxi drivers in Leeds to create a driver-owned app, and supporting community land trusts in Birmingham.

For the young Fahnbulleh, inequality was not an abstract concept. She was born in Liberia to a Liberian father and Sierra Leonean mother and witnessed “excruciating” poverty – “kids not eating for days on end” – as a kleptocratic elite looted the country’s resources.

Fahnbulleh also learned to resist injustice. Her father, who served as Liberian education minister and foreign affairs minister from 1978 to 1983, protested against corruption and “very quickly made his way on to the hit list”. In 1986, the year NEF was founded, Fahnbulleh fled Liberia with her family, who successfully claimed asylum in the UK. “He’s always been trying to fight the fight in a country that has the most tragic history; there’s inspiration in that,” said Fahnbulleh of her father.

The family lived in Tunbridge Wells, Kent, and Fahnbulleh studied politics, philosophy and economics at Oxford University, before achieving a Master’s and PhD in economic development from the London School of Economics in 2005. (In between, she worked in the advertising department of the New Statesman.)

After completing her academic studies, Fahnbulleh joined a development consultancy in Bosnia, establishing an economic and strategy unit in the president’s office. “I just remember coming out of the airport and everyone staring at me because it was not just a black person but a young, black girl on her own, which was pretty intimidating,” Fahnbulleh told me. “I had to go in and earn people’s respect and trust because they were like ‘who is this black kid?’”

She later served under three British prime ministers – Tony Blair, Gordon Brown and David Cameron – on the PM’s strategy unit and also worked for Ed Miliband as a policy adviser. Why does she believe his political project failed? “I wonder whether it was too soon… Most people can withstand pretty egregious circumstances for a few years but five, six, seven. That’s when it starts to bite in quite a defining and corrosive way.”

She added: “Labour during the Ed days was in quite a defensive mode. The sense that they still needed to build economic credibility, the deference to the austerity debate, which could have been challenged but wasn’t…There is a passion, there is a bolshiness now that feels quite different.”

A recent Prospect magazine article declared that “Jeremy Corbyn needs a think tank”. Does Fahnbulleh believe NEF could be it? “What NEF has done beautifully over the years is staying above politics,” she replied diplomatically.

But she praised John McDonnell’s “new economics” project as “incredibly encouraging” (McDonnell’s economic adviser James Meadway was formerly NEF’s chief economist) before cautioning against the automatic renationalisation of privatised services (water, energy, rail, post). “I’m not sure you can do it in one go, I’m not sure it would be desirable to. I think there’s far more power and viability in thinking about municipal and not-for-profit options.”

Fahnbulleh also referenced the “first incarnation” of Theresa May’s premiership (“when people like Nick Timothy were in No 10”) and its early emphasis on squeezed living standards. “Their analysis was correct. The big tragedy has been that agenda completely falling by the wayside.”

But she remained defiantly optimistic: “I don’t think the British public will suck up 15 years, if not longer, of wage stagnation without some kind of political retaliation.”