Sharecast - It said that in light of Jansen's forthcoming departure, its nominations committee had initiated a formal succession process to identify a suitable candidate for the role of chief executive.
The news came amid reports the FTSE 100 telecoms company was in the sights of its major shareholder Deutsche Telekom (ETR:DTEGn) for a possible takeover.
According to the Telegraph, the former phone monopoly was ramping up its work with advisers from Robey Warshaw and Goldman Sachs (NYSE:GS) on its defence, as rumours that the German giant - which already owns 12% of BT - was preparing an offer.
“Philip has done an excellent job in his time at BT, and the board is fully supportive of our long-term strategy which he and his team are pursuing,” said chairman Adam Crozier.
“Whilst we are still in the early years of that transformation we are on track to deliver.”
Crozier said the succession process to replace Jansen was something that the board was “well prepared for”.
He said all appropriate candidates were being considered, with the board expecting to update the market on progress over the summer.
Philip Jansen meanwhile said the company had made “a lot of progress” over the last four and half years.
“We're investing heavily in both BT's and the UK's future.
“We're building like fury, have now passed over 11 million homes with fibre, have got 5G service to 68% of the country and our customer service is much improved.
“This is creating a much stronger BT Group (LON:BT) which is starting to drive growth for both investors and the UK.”
Jansen said there was still more to do, adding that he was “fully committed” to driving the business forward until he handed over to his successor.
Reporting by Josh White for Sharecast.com.