The royal aide who made a bullying complaint against the Duchess of Sussex is to leave his role as chief executive of the Duke and Duchess of Cambridge’s Royal Foundation.

Jason Knauf worked for the Sussexes as their communications secretary when in October 2018 he emailed his concerns about Meghan to William’s then private secretary, in an apparent attempt to force Buckingham Palace to protect staff.

Later his “unequivocal” denial he helped Meghan write a letter to her estranged father helped her win her copyright claim against The Mail On Sunday which had published parts of the document, the High Court ruled.

The American-born former corporate affairs executive has worked for a range of institutions from the office of the New Zealand prime minister to HM Treasury and the Royal Bank of Scotland.

He became the communications secretary to the Duke and Duchess of Cambridge and Prince Harry in 2015 before leading the press team for Meghan and Harry.

Mr Knauf led a review of the Foundation’s role and structure from March 2019 before becoming its chief executive in September of that year.

During his time Mr Knauf oversaw the launch of the Foundation’s Earthshot Prize, William’s ambitious £50 million environmental prize which aims to recognise solutions, ideas and technologies that “repair the planet”.

He also steered the body’s response to the pandemic, establishing a response fund which saw £1.8 million granted to causes supporting frontline workers and the mental health needs of the nation.

William and Kate said about Mr Knauf, who leaves his post at the end of December: “We are immensely grateful for his hard work and commitment, both at the Royal Foundation and previously as our communications secretary.

“Since taking over as chief executive, Jason has driven positive change, making our vision for our charitable work and the causes that matter most to us a reality.

“We are sad to see him go but wish him all the very best in his future career.”

Mr Knauf said: “Working with the Duke and Duchess of Cambridge has been the privilege of my career.

“I will always be grateful for the opportunity I have had to support their leadership in the UK and internationally.”