BT's chief scientist, JP Rangaswami, has stepped down "in order to pursue other opportunities", after nearly five years with the company.
Rangaswami, an internationally acclaimed thought leader in the technology industry, joined BT in 2006 as CIO for its global services arm. Previously, he worked for Dresdner Kleinwort, where he was chief information officer for several years.
"We can confirm that JP Rangaswami decided to leave BT on 29 October in order to pursue other opportunities," BT said in a statement.
It said Rangaswami would continue to be involved with the company as a board member of Ribbit, a telecoms company in Silicon Valley, US, which was acquired by BT Group in 2008.
"Since joining over four years ago, JP has made a significant contribution to the business," said BT. "He leaves with our thanks and best wishes for the future."