The United Nations must do a better job at combating the root causes of violent extremism and global insecurity, Helen Clark, one of the frontrunners to succeed Ban Ki-moon as UN secretary general, has said.

With jitters rising around the world in the wake of recent attacks in Nice, France; Wurzburg, Germany; and Orlando, Dallas and Baton Rouge in the US, Clark said the UN was struggling over global security. “The UN is seen to be not doing so well on the peace and security front,” the former prime minister of New Zealand told the Guardian.

Clark said that the UN’s archaic bureaucratic structure was proving a drag on its ability to help in the fight against extremist attacks. “We have the tools from the middle of the last century to fight today’s battles, and we can do better than that.”

She said: “If we are going to effectively fight violent extremism it’s not just intelligence and security cooperation that’s important, it’s addressing the root causes. That takes you into development, human rights, peace-building: how can we get them to work in harmony to address these issues?”

Clark spoke to the Guardian in New York just days before the UN security council holds the first of three straw polls in which the 15 member states will begin to indicate their preferred candidates. At a time of unprecedented anxiety and fractiousness in politics – expressed in the UK’s Brexit decision to withdraw from Europe and the fear-mongering tactics of Donald Trump at the Republican national convention in Cleveland – her pitch for the top job in global governance is centering around her self-projection as a safe pair of hands.

“The UN needs someone with leadership ability, experience, judgment – someone who is predictable, practical, pragmatic, who likes to get results,” she said.

The approach is strikingly similar to that of Hillary Clinton in the US presidential race, where the former secretary of state is billing herself as the dependable option in an increasingly unstable world. Against that model stands the maverick rule-breaking volatility of the Trump campaign that is the polar opposite of a safe pair of hands.

So could a UN secretary general Helen Clark work with a US president Donald Trump?

Clark, who proved her political stamina and resilience by holding on to the premier’s position in New Zealand from 1999 to 2008, said her track record spoke for itself.

“It’s been my job in life to work with people with very different approaches,” she said. “In my time as prime minister I worked with George Bush for eight of the nine years, and John Howard for eight of the nine years.”

Since 2009 she’s been head of one of the UN’s most important departments, the development programme UNDP. Her tough approach to management efficiency and cutting budgets has won her plaudits from the US administration, the UN’s main funder, but prompted grumbling from within the institution.

Foreign Policy magazine recently carried a probe into Clark’s management style that reported widespread disgruntlement among staff. The article talked of a “trail of embittered peers and subordinates” in UNDP and told the story of an official who was allegedly driven out by Clark in retaliation for the employee’s participation in a critical review of the agency’s response to human rights abuses in Sri Lanka.

Clark denied that her reorgaisation of UNDP had been an internal disaster. She said the number of employment tribunals brought by individuals was “tiny, a handful”.

“One of the hardest things is to change an organisation, as people have a vested interests in the way things are. But not to do it, knowing that the whole nature of funding is changing and you have to be much more adaptable, is not an option – you have to act in the interests of the organisation.”

Clark also dismissed the claims about the allegedly retaliatory treatment of the official: “I have no evidence of that”. She said there were legitimate criticisms of the way the UN dealt with Sri Lankan abuses during the civil war with the Tamil Tigers, but said the conflict was officially declared over a month after she started at the helm of UNDP – “it was before my time”.

Being a self-avowed pragmatist, Clark knows better than to promise a radical restructuring of the UN security council with its 20^th-century dominance of the five permanent members – US, UK, France, Russia and China. The secretary general has no power to make such changes that could only come from the P5 itself.

But she did put in an appeal: “I hope member states will agree to reform, as the world is clearly not what it was in 1945. You have to make the UN more effective. If we didn’t have it today we’d have to invent it, and now that we’ve got it we have to reinvent, renovate, renew, overhaul it.”

She pledged to clamp down on crimes committed by UN peacekeepers amid the billowing scandal around sexual exploitation and abuse by troops in the Central African Republic. “No trooper going into these situations should be under any allusions of what the expectations and standards are. The slightest whiff of a problem, stand the person down, investigate. Blue helmets are set up to protect people, not to prey on them.”

And Clark promised to respect whistleblower protections where UN staff can safely sound the alarm on corruption or wrong-doing from within. “The point is listen hard: if there is any suggestion of wrongdoing, deal with it.”

This year’s selection process for Ban’s successor has been staged with unprecedented openness, with the 12 candidates engaging in public hustings for the first time. But with veto-wielding Russia indicating that it expects the job to go to one of the eight candidates from eastern Europe in accordance with Buggins’ turn, Clark is under no illusions about how the final decision will be made.

She says the new openness in the process spearheaded by the general assembly has thrown up a different kind of lead candidate, but it remains unclear whether that will result in a different kind of appointment.

“Will it be Buggins’ turn again? We don’t know it won’t be. All we know is that when the call went out there was no sub-clause saying ‘Don’t bother to apply if you’re not from X region’. Given the problems the world faces, surely you would have a global search for the best talent for this job. The focus has to be on the problems the UN has to face, and who is the best candidate to deal with them.”