Donald Trump sacks campaign manager Corey Lewandowski

Republican presidential candidate Donald Trump. Picture: Getty Images

Mr Lewandowski had been by Mr Trump’s side since the beginning of his unlikely rise to challenge to become the next Replublican president.

Mr Lewandowski had clashed with long-time workers brought in to make the campaign more professional.

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

Mr Lewandowski last night deflected any criticism of his approach, pointing instead to campaign chairman Paul Manafort. He said: “Paul Manafort has been in operational control of the campaign since 7 April. That’s a fact,”

Trump spokeswoman Hope Hicks described Mr Lewandowski’s departure as a “parting of ways.” And a source close to Mr Trump said Mr Lewandowski was forced out largely because of his poor relationship with the Republican National Committee.

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

Mr Trump was upset that so many Republicans – House Speaker Paul Ryan and senate majority leader Mitch McConnell among them – were reluctant to support him.

Mr Trump’s children were also reported to have had long-simmering concerns about Mr Lewandowski, who had limited experience on the national scale before becoming the billionaire’s campaign chief.

Some of Mr Trump’s children were among those urging the billionaire businessman to change tactics for the election.

“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.”

Mr Lewandowski has been a controversial figure in the campaign, but benefited from his proximity to the presumptive Republican nominee. Often mistaken for a member of the candidate’s security team, he travelled with Mr Trump on his private plane to nearly every campaign stop.