Almost half of senior executives and managers use e-mail three or more hours a day, according to a new survey by NFI research.

Forty-five percent of business leaders say they spend three or more hours a day reading, writing, sending or receiving e-mail with most of them using both computers and their phones for the work.

"E-mail is the great disruptor," said one respondent to the survey. "We must learn to ignore it, and then attack it two to three times per day at set intervals. Otherwise, we lose focus on our most important priorities."

Sixty percent of those working in large companies (10,000 or more employees) spend three or more hours on their e-mail compared to 38 percent of those in small companies (500 or fewer employees). Two times more of those in large companies than small spend more than four hours on e-mail.

NFI Research surveys senior executives and managers globally every two weeks.