Donald Trump has fired his hard-charging campaign manager, Corey Lewandowski, in a dramatic shake-up designed to calm panicked Republican leaders and reverse one of the most tumultuous stretches of Trump’s unconventional White House bid.

Lewandowski, in some ways as brash and unconventional as the candidate himself, had been by Trump’s side since the beginning of his unlikely rise to presumptive GOP nominee.

• Aussie tourists seriously injured in Vanuatu crash
• McGuire and Co show they’re ‘sorely out of step’
• Eddie, James: it’s time to go

But he clashed with longtime operatives brought in to make the seat-of-the-pants campaign more professional.

The former conservative activist played a central role in daily operations, fundraising, and Trump’s search for a running mate, but Lewandowski’s aggressive approach also fuelled near-constant campaign infighting that complicated Trump’s shift toward the general election.

Reached on Monday, Lewandowski deflected any criticism of his approach, pointing instead to campaign chairman Paul Manafort.

“Paul Manafort has been in operational control of the campaign since April 7. That’s a fact,” Lewandowski said, declining to elaborate on his dismissal.

Trump spokeswoman Hope Hicks described Lewandowski’s departure as a “parting of ways.”

A person close to Trump said Lewandowski was forced out largely because of his poor relationship with the Republican National Committee and GOP officials.

That person spoke on the condition of anonymity because the person was not authorised to discuss internal deliberations.

The move came as Trump faced continued deep resistance from many quarters of his party concerned by his contentious statements and his reluctance to engage in traditional fundraising.

Trump was upset that so many Republicans – House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell among them – were reluctant to support him, the person said, and at least partially blamed Lewandowski.

“Firing your campaign manager in June is never a good thing,” said veteran Republican operative Kevin Madden. “The campaign will have to show dramatic changes immediately on everything from fundraising and organising to candidate performance and discipline in order to demonstrate there’s been a course correction. Otherwise it’s just cosmetics.”

Lewandowski has long been a controversial figure in Trump’s campaign.

He was a chief promoter of the idea that the best campaign strategy was to “Let Trump be Trump.”

Lewandowski frequently dismissed the notion that Trump needed to hire more experienced political hands, spend on polling and sophisticated data operations, and moderate his rhetoric as he moved toward the general election.

That approach clashed with seasoned operatives hired in recent months.

Minutes after news of Lewandowski’s departure was announced, Trump aide Michael Caputo tweeted, “Ding dong the witch is dead!” and included a link to the song from the film, “The Wizard of Oz.”

Lewandowski was charged with misdemeanor battery in the spring for an altercation involving a female reporter during a rally.

The charges were later dropped. Trump defended Lewandowski throughout the episode and repeatedly framed his own actions as a sign of loyalty and a demonstration that he would not give in to outside pressure.

“Folks, look, I’m a loyal person,” Trump told voters at the time.

“It’s so important,” he said of loyalty in a subsequent interview. “And it’s one of the traits that I most respect in people. You don’t see it enough.”