The Secret Service has confirmed it will investigate comments made by Donald Trump’s longtime butler calling for President Obama to be killed.

“The US Secret Service is aware of this matter and will conduct the appropriate investigation,” agency spokesman Robert Hoback said in a statement.

Anthony Senecal, who worked as a butler to the presumptive GOP presidential nominee for 17 years, until 2009, wrote in a recent Facebook post that Mr Obama should be shot by the military as an “enemy agent.”

The Secret Service said it was aware of the comments allegedly made by the butler (Facebook)

“To all my friends on FB, just a short note to you on our pus headed “president” !!!! This character who I refer to as zero (0) should have been taken out by our military and shot as an enemy agent in his first term !!!!!“ Mr Senecal said in a Facebook post, according to Mother Jones magazine.

“Instead he still remains in office doing every thing he can to gut the America we all know and love !!!!!”

The magazine said that Mr Senecal, 84, who now works as the in-house historian at Trump’s Mar-a-Lago estate in Florida, has made multiple Facebook posts calling for Mr Obama’s death. Mr Senecal confirmed to Mother Jones that he had written the posts.

Last April, he wrote that the president should be hanged.

“Looks like that sleezey b**tard zero (O) is trying to out maneuvre Congress again, if the truth be known this prick needs to be hung for treason!!!” he said.

Like Mr Trump, Mr Senecal also argued that Mr Obama is not a United States citizen and is ineligible to serve as president.

Mr Senecal told The New York Times in a wide-ranging interview published in March that he worked as Mr Trump's butler for nearly 30 years. He has served as an unofficial historian at the estate since 2009, when he was relieved of his butler duties after Trump rejected his request to retire.

The article detailed Mr Senecal's intimate knowledge of everything from Trump's steak order to his sleep schedule, but gave no hints as to his political leanings.