Prime Minister Stephen Harper's director of communications, Angelo Persichilli, has quit after only seven months on the job, saying the demands on his time were too high.

In his letter of resignation, which was shared with the media, Persichilli said he would leave the job as soon as a successor is appointed.

"This is a prestigious position that requires extremely intense effort and very long hours, which at a certain age, are not an option for a long period of time," he wrote. The 63-year-old said it was an honour to serve Harper "during this exciting time."

CBC News has learned Persichilli was advised by his doctor in mid-February that he should take some time off, and his resignation does not come as a surprise to Harper. Persichilli told the prime minister about a week ago that he would be leaving the job.

He will be accompanying the prime minister on a trip to Washington next week and after his replacement is named he plans to take at least two months off to rest and get his health back on track.

Angelo Persichilli has resigned as Prime Minister Stephen Harper's director of communications, making him the sixth person to leave the job since 2006. (Twitter)

Persichilli's appointment in late August to the Prime Minister's Office surprised many because he was a political columnist at the time with The Toronto Star and Hill Times and because he doesn't speak French. He was also a long-time contributor to the Italian-Canadian newspaper Corriere Canadese.

Persichilli did much of his work for the last few months behind the scenes while Andrew MacDougall, Harper's associate director of communications, acted as the prime minister's spokesperson. Harper also has several press secretaries on his communications staff.

Persichilli's appointment raised eyebrows not only for his lack of French but because of some of his past writings on Quebec.

Persichilli's departure makes him the sixth person to leave the top communications job in Harper's office. The other people to hold the job were William Stairs, Sandra Buckler, Kory Teneycke, John Williamson and Dimitri Soudas.

Stairs worked for Harper before he was elected prime minister in 2006 and left the job soon after he took office. Buckler held the job for a little more than two years and resigned in 2008, followed by Teneycke, who worked for Harper for about a year and said when he left he wanted to spend more time with his young family and pursue other opportunities. Teneycke is now an executive with Sun News Network.

Williamson, a former federal director at the Canadian Taxpayers Federation, served briefly in the role before stepping down to run in the last election. He won his seat in New Brunswick.

Soudas, a loyal and longtime member of Harper's staff was promoted from associate director of communications to the top job in the spring of 2010 when Williamson left and he maintained the job until September. Soudas later took a job with the Canadian Olympic Committee.