He was the UN troubleshooter tasked with galvanising the world’s response to the Ebola epidemic and led the fight against cholera in Haiti, just as he did earlier against global pandemic flu. So on paper, David Nabarro may seem the ideal candidate to become the world’s most powerful doctor.

In practice, the Briton faces a stiff contest, with five other candidates also vying to take over from Margaret Chan in May 2017 as head of the World Health Organisation, the troubled UN body much criticised for its slow response to the 2014 Ebola outbreak. The job has always in the past been decided between governments trading political alliances behind closed doors. But this time, with the WHO’s credibility still on the line, Nabarro and his allies think his CV may be the right one.

“I’m actually a doer who delivers,” Nabarro in an interview with the Guardian. “And a doer who is not scared of being accountable at all times. And I think that is known.”

Nabarro, sitting in the London office of the chief medical officer, Prof Dame Sally Davies, has the support of the UK government.Davies says Nabarro is uniquely well-qualified and that will be recognised at a time when the WHO badly needs the best possible leader.

“I think he’s likely to get it because he’s the best candidate, and at the end of the day I’m hopeful that the politics will fall aside and the best person will come through,” she says.

Davies, who has the British seat on the WHO’s executive board, points to an editorial she co-authored with other board members in the Lancet in January, describing the criteria for nomination as DG. They include high-level public health and international health experience, excellent communication, leadership skills and commitment. Quite simply, she says, Nabarro has all of them.

This is not about favouring the UK. “In fact, David might not always do what I would want because he is independent and thoughtful in his own way,” she says. “It is about having a strong leader for the WHO who understands the changing global architecture and the needs of low- and middle-income countries, particularly around two things – emergency response and the SDGs [sustainable development goals] – and can work effectively with ministers and prime ministers.”

Above all, Davies and others are concerned that the reforms of the WHO, in which Nabarro has already been centrally involved, should be implemented to make the institution stronger and fit for purpose as the world’s bulwark against devastating outbreaks of infectious diseases, as well as malnutrition and chronic diseases caused by obesity and changing lifestyles.

The future of the WHO was in question after its failure to spot and close down Ebola early enough in west Africa, which led to a global crisis. All the reports written in the aftermath said that if it were to survive, the organisation needed stronger and more focused leadership in emergencies.

Nabarro led the UN response to bolster the WHO as the envoy of the outgoing UN secretary-general, Ban Ki-moon, and afterwards chaired the advisory committee on reform that Chan set up. A lot of excellent innovations have strengthened the organisation in the past year or two, but it is not yet in good enough shape, he says.

“The new health emergencies programme that we advised on and that’s being implemented, which is a cross-organisation programme with single cadre of staff, single budget, single performance standards, clear lines of responsibility, is being built up,” he says.

“But it also needs to be properly financed – and at the moment it’s not. And so we need to get the money, improve performance, get more money, improve performance more. It’s about a five-year project and I personally would like to be moving more quickly on that because we never know when the next outbreak is going to come. We had a bit of a scare this year with yellow fever and I want to be sure that this is done quickly.”

The WHO needs to be one unified organisation. Ebola exposed the fracture lines between the regions, with Africa failing to communicate with the Geneva HQ. Davies says all staff have to be appointed on merit, not as a political favour to governments, and they must not be advocates for any specific interest.

Health workers prepare to enter the house of a person suspected to have died of Ebola on the outskirts of Freetown, Sierra Leone. Photograph: Michael Duff/AP

Nabarro agrees there must be no more fiefdoms. “Part of that is ensuring that all staff are appointed on merit. Part of it is about ensuring they are not just pursuing money for their own interests and part of it is ensuring that they find the organisation something that they believe in and are prepared to work for it as an entire organisation,” he says.

It’s a culture change but it also depends on having enough money, so that WHO staff do not think they have to bargain with governments, organisations or special interest groups to raise it.

The WHO’s finances are a difficult issue. The amount given by governments for general purposes has steadily declined. The coffers have been topped up by voluntary donations from specific governments or organisations, such as the Gates Foundation, that are tied to particular projects. The UK is the third biggest donor, says Davies, and some of the money is for priorities that are agreed with the WHO, but, she says: “I think I would like to see, personally, an increase in the subscription, so that there is less voluntary funding and more that is just routine and under the absolute direction of the DG.”

Nabarro’s solution is for the organisation to become what he calls “catalytic”. It does not have the money to do everything that is needed. There are many health organisations as well as healthcare systems in every country. The WHO can lead and encourage them to do what is needed, like the conductor of an orchestra, rather than doing it itself.

Chan has been was a technocrat, maintaining that her role was to carry out the bidding of member states, while Norwegian former prime minister Gro Harlem Brundtland was criticised when she held the job for telling countries in no uncertain terms what they should do. Nabarro, who once worked for Brundtland when she was DG, diplomatically says he is a bit of each of these leaders but also his own person, able to court consensus on issues such as anti-tobacco treaties while taking tough decisions if necessary in emergencies.

Whether that pleases the voting governments will be seen at the end of January, when the six will be reduced to a shortlist of three, and then in May when the puff of white smoke goes up at the World Health Assembly in Geneva.