The ex-deputy Liberal party leader has also warned rising inequality is behind populist lurches towards protectionism and that anti-free trade policies could lead to economic depression.

Ms Bishop told a summit of public sector women in leadership in Canberra on Wednesday the last decade's "revolving door" of prime ministers made Australians believe MPs put personal ambition before the national interest.

"I know it was more complicated than that, and each circumstance was different. But nevertheless, there was this overriding sense that 'this is all about those politicians' personal ambition and not about me, a member of the public'," she said.

"You can see how the disillusionment has set in."

Ms Bishop was foreign minister through the Coalition's share of the leadership turmoil, remaining deputy Liberal leader after a spill removed Tony Abbott as prime minister in 2015.

She left politics this year following Malcolm Turnbull's political demise, and after an unsuccessful tilt at the leadership, in August 2018.

Ms Bishop said broken promises had also undermined public faith in politics.

"I know there's a natural antipathy towards figures of authority in Australia, they have a scepticism about others telling them what to do," she said.

"But I also think that politicians have themselves to blame, and when you make promises and then don't keep promises, the Australian public have a reason to be cynical."

Ms Bishop said only genuine obstacles would justify government decisions not to fulfill promises, such as a "crisis".

"It has to be explained in honest and frank terms, otherwise the disillusionment sets in," she said.

"It's all about managing expectations as well, being honest about what governments can and cannot do. There's nothing worse than over-promising and under-delivering, and that's what we've seen so often."

She said despite pressure on federal governments to increase subsidies for the car manufacturing industry before it left Australia, one company told her its decision was influenced by declining sales as consumers turned to cheaper imports.

"Yet no one had a conversation with the Australian people to say 'the individual choices that you make as consumers can have as much of an impact on the Australian economy as any policy that the government might come up with'," she said.

Ms Bishop said she was disturbed by Pew Research Center survey results showing 19 per cent of Australians said it would be good to be ruled by a strong leader without parliament or courts and 12 per cent liked the idea of military rule.

She was also concerned that only 7 per cent of Australians strongly believed the federal government would do the right thing by the country.

"We are seeing this played out around the world and support for a political system depends upon the social contract that supports the hopes and aspirations of the people," she said.

"Now people don't expect all their hopes and all their aspirations to be met, but if they're never met, then they lose faith in the system, and they're looking for alternatives, and they're looking for answers that governments can't give them.

"That's why we're seeing the rise of populism. Inequality is increasing around the world. The gap between the haves and have-nots is increasing, and that inequality where people feel they're missing out on the benefits that others are enjoying leads to sentiments against globalisation - anti-globalisation, anti-capitalism, anti-technological advancements, because they think they threaten jobs.

"Politicians want to give answers and that's where populism comes in."

Populists were offering simplistic answers to complex questions, and the first "port-of-call" was protectionism, Ms Bishop said.

"History has shown time and time again that protectionism leads to a downturn in the economy, it can lead to recession or depression," she said.

"We know that open, freer markets lead to greater national wealth, yet it's so easy to argue 'I can protect your job by putting up barriers' and it's a thankless task to try and argue the benefits of open, free, liberal markets."

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Ms Bishop said while Australia's standard of living depended on its ability to sell its goods and services around the world, protectionism was "creeping into discussions".

Australians would welcome a conversation on how decisions were made in the nation "within an ethical framework, a principled framework" so that it could "move away from any suggestion of populism".

She said an example of a policy that needed a "very honest" discussion was taxation and the levels needed for the services and economic activity Australians expected.

"We have to be honest about what governments can and can't do and make these decisions within an ethical and principled framework.

"That means that all people who work in the government as public servants, as politicians, have to keep close to the communities we're serving, understanding their needs, their requirements, but being close enough to be able to explain what can and can't be done."