The account move is a major vote of confidence in Fallon and will provide the agency with its first opportunity to produce BT advertising that will run in the UK.
However, Amanda Mac-kenzie, the director of marketing services at BT, said the account move would not mean a loss of income for AMV.
"We are in the process of awarding additional business to all three of our agencies," she explained.
"The way we like to think of our roster is not on a like-for-like basis. They each have a particular role and we value them equally. Projects are assigned based on our strategic need so it is essential that we have a collaborative roster."
It has yet to emerge which agency will land the £12 million account for BT Yahoo! Broadband. It had been handled by Clemmow Hornby Inge until the agency parted company with BT in November 2003, owing to conflict.
BT launched its drive to increase the uptake of broadband in October 2002 with a £1-million-a-day campaign spearheaded by St Luke's special effects-laden television commercial, featuring animals escaping from a broadband pipe.
Following the launch, subsequent executions in the campaign were developed by AMV, including recent television work demonstrating the use of webcams.
Last week, BT announced it had met its 2004 target of two million wholesale broadband connections in the first two months.
Cilla Snowball, the chief executive of AMV, said: "This is part of a reallocation that will mean a net gain for everyone."
- Live Issue, p16.