Mavericks like Donald Trump and Nigel Farage are more trusted by the public because they don’t speak like politicians, a leading language expert claims.

The political class who start speeches with reassuring phrases such as ‘If I’m honest’ and ‘let me be clear’ actually make them appear less honest.

Research found “traditional” politicians such as Theresa May and David Cameron, who use cliches such as ‘the honest truth is’ and ‘believe me’, are more likely to arouse suspicion from the public.

But leaders who haven’t been trained in ‘politics speak’ such as Donald Trump, Nigel Farage and Jeremy Corbyn are more likely to be considered trustworthy, with 83 per cent of people surveyed saying they are more likely to trust someone using clear and uncomplicated language.

John Blakey, author of The Trusted Executive, who contributed to research, said: “Traditional leaders from the older generation, like Theresa May and David Cameron, have been trained to use these cliches since the start of their careers, but the problem is they no longer work.

“While the political elite try to mask their true feelings, political mavericks like Jeremy Corbyn and Donald Trump speak straight from the heart because they haven’t had any professional training.

“What our research shows is that people seem to respond to more authentic, more engaging language and are more likely to be suspicious of politicians who talk in managerial cliches.”

The reassuring phrases most likely to backfire are the Blairite ‘If I’m honest’, ‘let me be clear’ and ‘believe me’, according to the survey.

And ‘the honest truth is’, ‘the fact is’ and ‘to be fair’ are also likely to rouse suspicion.

The survey also found that 57 per cent were also more likely to believe someone giving short concise answers rather than going into more detail.

Mr Blakey said mainstream politicians like Theresa May could win back the trust of voters by being more frank and open.

He said: “Using political cliches is just a bad habit and with practice it can be stamped out.

“If mainstream politicians start to recognise that the way they’re talking isn’t working, then they can start the journey to appearing more authentic.

“Theresa May and David Cameron need to strip themselves back until they find a raw way of speaking.

“They need to find who they were before they were trained politicians and show their authentic selves.”

He said recent advances in technology have left the public wanting a more open and honest leader.

He said: “I would say transparency is the single word that can explain what’s going on here.

“Now that we have widespread globalisation and advances in social media, we’ve been given more broader access to the truth about what’s happening around the world.

“Having more access to the truth has left people seeing things they don’t like and now their default position is to be distrustful.

“Whereas we used to trust what the Prime Minister said just because they’re the Prime Minister, now we think: ‘You need to prove to us that you’re telling the truth’.”

He said people seen as “outsiders”, such as Nigel Farage, have an advantage over mainstream politicians because they talk in a different way.

He said: “Nigel Farage is already one step ahead of May because he doesn’t have to prove that he’s different from leadership in the past.

“The way he avoids complicated language and appears to speak from the heart appeals to people.”

They also found that the three qualities that are most important to appearing trustworthy are emotional openness, calm rationality and kindness.

And displays of aggression, competitiveness and outspokenness were likely to cause people to question the trustworthiness of public figures.

Mr Blakey said: “Despite what is commonly believed, kindness is an important ingredient in winning trust.

“If a leader is kind, it generates a feeling of companionship and convinces people that they are ‘one of us’.”

Gina Lodge, CEO of the Academy of Executive Coaching, who conducted the survey, said: “If someone repeatedly has to reassure you that what they are saying is true, that is an instant red flag that they are trying to mislead you.

“Similarly, a long, complicated answer is likely to be seen as evasiveness, trying to find a way to avoid telling the truth without actually lying.”​

She said Donald Trump appeals to people because he wasn’t afraid to speak unprofessionally about his competition.

She added: “During the election campaign, we saw how Trump deliberately used provocative language in his speeches.

“But he also used openly emotional language.

“He talked about his opponents being ‘mean’ to him or making ‘rude’ comments.

“He avoids speaking in managerial clichés and uses simple, direct language.

“This, more than the meaning of what he says, is why he was able to connect with people in such a powerful way.”