The telecoms company had been reviewing its options following a "mutual agreement" to end the relationship with PHD due to the agency's conflicting Yell and Pipex business.
PHD had three planners working on the business, the bulk of which was communications planning focused.
BT has a significant in-house media resource under its head of media Steve Huddleston. Reports had suggested that BT would move the business into its buying agency Starcom but BT decided against this.
A BT spokesman confirmed the decision to take the media planning account in-house.
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